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Concordance between administrative claims and registry data for identifying metastasis to the bone: an exploratory analysis in prostate cancer

  • Eberechukwu Onukwugha1Email author,
  • Candice Yong1,
  • Arif Hussain2, 3,
  • Brian Seal4 and
  • C Daniel Mullins1
BMC Medical Research Methodology201414:1

DOI: 10.1186/1471-2288-14-1

Received: 17 May 2013

Accepted: 20 December 2013

Published: 2 January 2014

Abstract

Background

To assess concordance between Medicare claims and Surveillance, Epidemiology, and End Results (SEER) reports of incident BM among prostate cancer (PCa) patients. The prevalence and consequences of bone metastases (BM) have been examined across tumor sites using healthcare claims data however the reliability of these claims-based BM measures has not been investigated.

Methods

This retrospective cohort study utilized linked registry and claims (SEER-Medicare) data on men diagnosed with incident stage IV M1 PCa between 2005 and 2007. The SEER-based measure of incident BM was cross-tabulated with three separate Medicare claims approaches to assess concordance. Sensitivity, specificity and positive predictive value (PPV) were calculated to assess the concordance between registry- and claims-based measures.

Results

Based on 2,708 PCa patients in SEER-Medicare, there is low to moderate concordance between the SEER- and claims-based measures of incident BM. Across the three approaches, sensitivity ranged from 0.48 (0.456 – 0.504) to 0.598 (0.574 - 0.621), specificity ranged from 0.538 (0.507 - 0.569) to 0.620 (0.590 - 0.650) and PPV ranged from 0.679 (0.651 - 0.705) to 0.690 (0.665 - 0.715). A comparison of utilization patterns between SEER-based and claims-based measures suggested avenues for improving sensitivity.

Conclusion

Claims-based measures using BM ICD 9 coding may be insufficient to identify patients with incident BM diagnosis and should be validated against chart data to maximize their potential for population-based analyses.

Keywords

Metastasis Bone SEER Claims Concordance

Background

Among men diagnosed with prostate cancer (PCa), seventy to eighty percent of those with metastatic disease have involvement of the bone [14] with significant implications for pain, morbidity and mortality [2, 58]. Increasingly, researchers are using claims-based measures of bone metastasis (BM) to examine incidence, associated costs, and survival [4, 6, 7, 9, 10]. These real world data, including the billing codes such as the International Classification of Diseases, 9th Revision Clinical Modification (ICD-9-CM) codes, reflect clinical practice but do not provide a consistent means of verifying the accuracy of clinical diagnoses. Using the Surveillance, Epidemiology and End Results (SEER) registry and linked Medicare claims available from the National Cancer Institute, we undertook the present study in an effort to better understand the concordance between registry-based data on BM and claims-based measures of BM, using men diagnosed with incident metastatic PCa as a model. To our knowledge, this is the first study to investigate the agreement between claims-based and registry-based sources of BM.

Evidence regarding the validity of using claims data to identify cancer stage, progression, and metastasis is not favorable [1113]. Moreover, the validity of using claims data to identify patients with BM may differ depending on the approach used. Previous studies have identified patients with BM based on the presence of a diagnosis of “secondary malignant neoplasm of bone and bone marrow” (ICD-9-CM 198.5) in claims data. These claims-based approaches differ in terms of the incorporation of the ICD-9-CM codes, for example, whether the codes should be present alone or with other procedure codes used to diagnose or treat BM. Several studies have defined BM patients as persons with two or more encounters including 198.5 anytime on or after the date of the first claim with a diagnosis of cancer [4, 9, 10]. Other studies have defined BM patients as persons with at least one inpatient claim with the 198.5 code, at least one outpatient claim with the 198.5 code paired with a code for procedures used to diagnose or treat BM, or at least one outpatient physician evaluation and management claim with the 198.5 code [6, 7].

Prior studies have reported BM prevalence using SEER cancer registries data linked with Medicare enrolment and claims files. The SEER data has traditionally provided AJCC metastasis information to confirm the incident staging of M1 (distant metastasis) or M0 (no distant metastasis). Starting in 2004, SEER adopted the Collaborative Stage (CS) system and SEER registries started to provide detail regarding the sub-stages of M1 disease: M1a (non-regional lymph nodes), M1b (bone), and M1c (other site, with or without bone disease). This SEER variable has not been validated and is generally not considered a gold standard for identification of the site of metastatic disease. As researchers consider its use in population studies involving SEER-Medicare data, information regarding the agreement between the M1b measure and claims-based data will be important to consider. The availability of registry-based information regarding incident BM diagnosis from SEER provides the opportunity to investigate the agreement between claims-based and registry-based measures of BM.

The objective of this study was to determine the concordance between the SEER registry measure of an incident BM diagnosis and the claims-based measures of BM-related health services utilization around the time of diagnosis. A secondary objective was to identify claims-based measures that could enrich claims-based BM approaches. These objectives are intended to support consistency in the use of claims-based BM approaches and support a more transparent and reliable approach to the development of claims-based approaches for studying cancer treatments and outcomes.

Methods

Data

This retrospective analysis of linked cancer registry and Medicare claims data included men at least 66 years of age diagnosed with incident PCa between 2005 and 2007 as listed in the SEER cancer registry. Cases were limited to those diagnosed with stage IV metastatic (M1) disease as identified by the American Joint Committee on Cancer Tumor-Node-Metastasis (AJCC-TNM) stage, 6th edition [14]. Claims data from 2004 to 2009 were extracted from linked Medicare claims files. The requirement for continuous enrollment in Medicare Parts A and B during the 12 months prior to and including the month of diagnosis constituted an additional inclusion criterion. Exclusion criteria were: 1) health maintenance organization (HMO) enrollment during the 12 months prior to and including the month of diagnosis since HMO claims can be unreliable due to missing data; 2) history of other cancers within 5 years prior to PCa diagnosis. Patients were censored if they enrolled in an HMO or lost Part A and/or B enrollment at any time following the diagnosis date, or if the end of the study period (December, 2009) was reached. This study was approved by the University of Maryland Baltimore Institutional Review Board (#HP-00049426).

Variables

Measures of bone metastasis diagnosis or associated health utilization

Patients were identified as having a SEER-based measure of BM if the AJCC metastatic component in the Collaborative Stage (CS) coding system indicated ‘M1b’ status, i.e. metastasis to bone at diagnosis. In defining the study cohort, we excluded the first year (i.e. 2004) in which the M1b measure became available in order to avoid possible coding problems that could have arisen as cancer registries gained familiarity with furnishing the M1b code. We investigated differences between three claims-based approaches to identify patients with BM-related claims (see Figure 1). We created a ‘generous’ approach (Approach 1), adopted an approach that is similar to the approach used in previous studies [6, 7] (Approach 2), and created a more restrictive approach (Approach 3) as follows:

Approach 1
https://static-content.springer.com/image/art%3A10.1186%2F1471-2288-14-1/MediaObjects/12874_2013_Article_1160_Fig1_HTML.jpg
Figure 1

Identification of patients with bone metastasis* using Medicare inpatient, outpatient, and carrier claims. *Patient identified to have bone metastasis if patient has claims-based evidence of bone metastasis from inpatient or outpatient or carrier claims. **ICD-9 diagnosis code of 198.5 represents ‘secondary malignant neoplasm of bone and bone marrow’.

At least one inpatient, outpatient, or carrier claim with an ICD-9 diagnosis code of 198.5 (‘secondary malignant neoplasm of bone and bone marrow’) in any diagnosis field.

Approach 2

At least one inpatient claim with an ICD-9 diagnosis code of 198.5 as the primary or secondary discharge diagnosis; OR at least one outpatient claim with a diagnosis code of 198.5 paired with a code for procedures used to diagnose or treat BM such as bone scan, bone biopsy, and/or use of intravenous bisphosphonate; OR at least one outpatient physician claim with a diagnosis code of 198.5.

Approach 3

At least one inpatient claim with an ICD-9 diagnosis code of 198.5 in any diagnosis field; OR at least two outpatient claims within a 90-day window with a diagnosis code of 198.5.

For each of the three approaches, patients were classified as having concurrent BM-related claims if claims submitted in the month before, during, or after the month of PCa diagnosis satisfied the condition stipulated by the approach. The exact date of diagnosis is not available from the SEER data and Medicare claims relevant to an event occurring in a particular month can appear in the month prior to and following the month in which the event occurred [15]. Figure 2 provides a graphical representation of ‘concurrent BM’-related claims, i.e. BM-related claims that were considered to be concurrent with the PCa diagnosis. The 3-month (90-day) window has been used in previous studies to define concurrent BM [6].
https://static-content.springer.com/image/art%3A10.1186%2F1471-2288-14-1/MediaObjects/12874_2013_Article_1160_Fig2_HTML.jpg
Figure 2

Identification of concurrent bone metastasis and bone metastasis ever using claims data.

Demographics and health care utilization measures

Patient-level demographic and clinical variables obtained from the SEER files include age, race, marital status, urban residence, prostate specific antigen (PSA) level and tumor differentiation at diagnosis. We assessed comorbid illness using the Charlson Comorbidity Index (CCI) [16] and the National Cancer Institute (NCI) Combined Index [17] using claims from the 12-month period before the month of diagnosis. Treatment receipt, use of health services such as bone biopsy, and bone or joint imaging, PSA tests, and cancer specialist visits were identified from MEDPAR and Part B claims.

Statistical analysis

Cross-tabulations of the claims-based BM approaches and the SEER-based measure of BM were used to compare concordance. We calculated sensitivity, specificity, and positive predictive value (PPV) for each approach compared to the M1b measure from SEER. Sensitivity for each claims-based approach was calculated as the proportion of patients with a SEER-based BM diagnosis who were identified to have BM-related utilization in Medicare claims. Specificity for each claims-based approach was calculated as the proportion of patients without a SEER-based BM diagnosis who also did not have BM-related utilization in Medicare claims. Positive predictive value was calculated as the proportion of patients with claims-based BM-related utilization who had incident BM diagnosis based on registry data.

In order to investigate the possibilities for improving sensitivity, we selected the measure with the lowest sensitivity for use in subsequent analyses. The chi-square test identified statistically significant differences in health services utilization between patients grouped with respect to: (1) presence or absence of concurrent BM-related health services utilization according to the claims-based approach; and (2) presence or absence of BM at diagnosis according to the SEER-based measure of BM.

To identify additional measures that could enhance the sensitivity of claims-based approaches, the sample with SEER-based evidence of BM was stratified by the presence or absence of concurrent BM according to claims-based Approach 3. Among this sample of patients with a diagnosis of BM based on registry data, the objective was to identify health resource utilization categories that are commonly reported among patients without BM-related claims. Utilization categories meeting these criteria can be used to improve the sensitivity of definitions created to identify men with an incident diagnosis of BM and/or with a diagnosis of BM outside the diagnosis window using health care claims data. We conducted sensitivity analysis focused on improving the sensitivity of Approach 3.

Results

Descriptive results

After applying study inclusion and exclusion criteria, the final study sample included 2,708 men diagnosed with incident stage IV metastatic PCa. Descriptive statistics for the full sample are presented in Table 1. The concordance between the two measures was captured using sensitivity, specificity, and PPV. The sensitivity, specificity, and PPV of the three claims-based approaches compared to the SEER-based measure of BM are presented in Table 2. The receipt of radiation (any type), external beam radiation therapy, radiopharmaceutical therapy, and intravenous bisphosphonate therapy at any time following diagnosis was higher among individuals with BM according to either SEER-based or claims-based measures. In terms of diagnostic tests, the receipt of bone or joint imaging at any time following diagnosis was higher among individuals with BM according to either SEER-based or claims-based measures. The SEER-based and claims-based measures were not consistent in terms of the relationship between physician visits (i.e., medical oncologists, radiation oncologists) and BM.
Table 1

Descriptive statistics for men diagnosed with metastatic prostate cancer between 2005 and 2007 (N = 2,708)

 

                 N

                %

Race/Ethnicity

  

 White non-Hispanic

2096

77.4

 African American non-Hispanic

326

12.0

 Hispanic

159

5.9

 Other

127

4.7

Age

  

 66-69

375

13.9

 70-74

499

18.4

 75-79

555

20.5

 80-84

645

23.8

 85+

634

23.4

Married

1583

62.3

Urban location

2396

88.5

High PSA at baseline

2298

84.9

Poorly differentiated tumor

1638

60.5

Charlson Comorbidity Index

  

 Zero

1453

53.7

 One

547

20.2

 Two or higher

470

17.4

 Missing

238

8.8

National Cancer Institute (NCI) Combined Index

  

 Zero

1459

54.2

 0-2

943

35.0

 > = 2

53

2.0

 Missing

238

8.8

Bone metastasis

  

Bone metastasis diagnosis

  

 SEER registry

1694

62.6

Bone metastasis – related utilization

  

 Claims – BM Concurrent, Approach 1

1481

54.7

 Claims – BM Concurrent, Approach 2

1363

50.3

 Claims – BM Concurrent, Approach 3

1198

44.2

Table 2

Sensitivity, specificity, and positive predictive value (PPV) of three claims-based measures defined concurrently with diagnosis of prostate cancer

 

Claims-based measure of BM-related utilization concurrent with diagnosis

 

Approach 1

Approach 2

Approach 3

Sensitivity (95% CI*)

0.598 (0.574 - 0.621)

0.555 (0.531 - 0.579)

0.480 (0.456 - 0.504)

Specificity (95% CI*)

0.538 (0.507 - 0.569)

0.584 (0.553 - 0.614)

0.620 (0.590 - 0.650)

PPV (95% CI*)

0.684 (0.660 - 0.708)

0.690 (0.665 - 0.715)

0.679 (0.651 - 0.705)

*95% confidence intervals were calculated using the Clinical research calculator from VassarStats[18] based on: Newcombe, Robert G. “Two-Sided Confidence Intervals for the Single Proportion: Comparison of Seven Methods”, Statistics in Medicine, 17, 857–872 (1998).

Subgroup comparisons based on health care utilization in full sample

Approach 3 was considered to be the best approach amongst the three options because, relative to the other two approaches, it relaxed the criteria based on inpatient claims (the coding of which is generally considered reliable) and at the same time tightened the criteria based on outpatient claims (the coding of which may be problematic for identifying clinical conditions). Approach 3 had the highest specificity, and thus performed best at excluding individuals who were false positives. On the other hand, it had the lowest sensitivity, i.e. a higher number of false negatives. Subsequent analyses sought to identify measures that could be used to supplement Approach 3, with the goal of reducing the number of false negatives.

Table 3 shows the proportion of patients with post-diagnosis health services utilization in terms of diagnostic testing/surveillance procedures and physician visits, stratified by presence of claims-based concurrent BM-related utilization and presence of SEER-based incident BM diagnosis. Proportions were reported as column percentages.
Table 3

Proportion of patients with post-diagnosis health services utilization, stratified by alternative bone metastasis measures

  

Claims Approach 3

SEER measure

Full M1 sample

Concurrent BM

No concurrent BM

 

BM at diagnosis

No BM at diagnosis

 

N = 2,708

N = 1,198

N = 1,510

 

N = 1,694

N = 1,014

 

(44.2%)

(55.8%)

(62.6%)

(37.4%)

 N

  Col%

 N

  Col%

 N

  Col%

P-value

 N

  Col%

 N

  Col%

P-value

Post-diagnosis resource utilization (i.e., till end of follow-up)

            

 Bone mineral density (BMD)

109

4.0

40

3.3

69

4.6

0.11

71

4.2

38

3.8

0.57

 Test

 PSA test

2,148

79.3

906

75.6

1,242

82.3

<0.01

1,389

82.0

759

74.9

<0.01

 Oncologist visit

1,681

62.1

857

71.5

824

54.6

<0.01

1,041

61.5

640

63.1

0.39

 Nuclear medicine specialist

NR

NR

NR

+

NR

-

0.07

NR

>0

NR

0.0

0.01

 Visit

 Radiation oncologist visit

1,066

39.4

528

44.1

538

35.6

<0.01

687

40.6

379

37.4

0.10

 Bone biopsy

79

2.9

62

5.2

17

1.1

<0.01

47

2.8

32

3.2

0.57

 Bone or joint imaging

2,200

81.2

1,006

84.0

1,194

79.1

<0.01

1,406

83.0

794

78.3

<0.01

Treatment receipt (Part B)

            

 Radiation

889

32.8

445

37.2

444

29.4

<0.01

581

34.3

308

30.4

0.04

 External Beam radiation

839

31.0

425

35.5

414

27.4

<0.01

553

32.6

286

28.2

0.02

 Therapy

 Radiopharmaceutical therapy

91

3.4

60

5.0

31

2.1

<0.01

72

4.3

19

1.9

<0.01

 Bisphosphonates IV

862

31.8

494

41.2

368

24.4

<0.01

593

35.0

269

26.5

<0.01

 Erythropoietin

535

19.8

274

22.9

261

17.3

<0.01

352

20.8

183

18.1

0.08

 Opioids (moderate-severe)

624

23.0

248

20.7

376

24.9

0.01

379

22.4

245

24.2

0.28

  

Claims Approach 3

SEER measure

Full M1 sample

Concurrent BM

No concurrent BM

 

BM at diagnosis

No BM at diagnosis

 

N = 2,708

N = 1,198

N = 1,510

 

N = 1,694

N = 1,014

 

(44.2%)

(55.8%)

(62.6%)

(37.4%)

 N

  Col%

 N

  Col%

 N

  Col%

P-value

 N

  Col%

 N

  Col%

P-value

Resource utilization during the 90-day diagnosis period

            

 PSA test

1,629

60.2

698

58.3

931

61.7

0.07

1,046

61.8

583

57.5

0.03

 Bone biopsy

65

2.4

NR

+

NR

-

<0.01

42

2.5

23

2.3

0.73

 Bone or joint imaging

2,009

74.2

999

83.4

1,010

66.9

<0.01

1,317

77.7

692

68.2

<0.01

 

Mean

S.D.

Mean

S.D.

Mean

S.D.

p-value

Mean

S.D.

Mean

S.D.

p-value

Post-diagnosis resource utilization (i.e., till end of follow-up)

            

 Number of BMD tests

0.04

0.21

0.03

0.19

0.05

0.22

0.09

0.04

0.22

0.04

0.19

0.39

 Number of PSA tests

8.16

10.01

8.26

10.77

8.08

9.38

0.63

8.81

10.41

7.07

9.21

<0.01

 Number of PSA tests among patients with PSA tests

10.29

10.23

10.93

11.15

9.82

9.47

0.02

10.75

10.56

9.44

9.54

<0.01

 Number of bone biopsies

0.03

0.18

0.05

0.24

0.01

0.11

<0.01

0.03

0.18

0.03

0.19

0.53

 Number of bone or joint imaging

1.65

1.58

1.67

1.56

1.64

1.61

0.60

1.73

1.61

1.52

1.53

<0.01

Resource utilization during the 90-day diagnosis period

            

 Number of PSA tests

0.89

0.92

0.92

1.01

0.86

0.84

0.07

0.92

0.94

0.83

0.89

0.01

 Number of bone biopsies

0.02

0.16

0.05

0.23

0.003

0.06

<0.01

0.03

0.17

0.02

0.15

0.60

 Number of bone or joint imaging

0.76

0.47

0.86

0.42

0.68

0.49

<0.01

0.79

0.44

0.70

0.49

<0.01

NR, Not reported due to small sample size, per data use agreement; ‘+’ means that the column% is greater than the percentage for the full sample while ‘-‘ means that the column% is smaller than the percentage for the full sample.

Examining percentages and how they differ across groups defined using the claims-based approach and the SEER-based measure facilitates the identification of measures that could be used to reduce the number of false negatives identified by the claims-based approach. The relevant measures would be positively associated with a BM diagnosis and negatively associated with claims-based evidence of BM-related utilization. Utilization of PSA tests and the intensity of use of PSA tests could be useful in this regard. The proportion of patients with a claim for a PSA test and the mean number of PSA claims per person were each statistically significantly higher among patients with SEER-based BM diagnosis compared to patients without SEER-based BM diagnosis when considering utilization at any time. In contrast, the proportion of patients with any PSA test at any time during the follow-up period was statistically significantly lower among patients with claims-based evidence of concurrent BM-related utilization compared to patients without claims-based evidence of concurrent BM-related utilization. Consideration of utilization during the diagnosis period, rather than at any time, could be particularly useful when the focus is on identifying individuals with incident BM. Results for tests or procedures occurring within the 90-day diagnosis period are provided in the last section of Table 3.

Subgroup comparisons based on health care utilization among M1b patients

Differences between patients grouped according to concurrent claims-based BM-related utilization were examined among patients with an incident BM diagnosis. Utilization that is positively correlated with the M1b measure (Table 3) and negatively correlated with the concurrent claims-based BM-related utilization measure could be used to supplement Approach 3 so as to reduce false negatives. The likelihood and frequency of bone or joint imaging during the diagnosis period was higher among individuals with BM according to SEER (Table 3). Among the 1,694 patients, the likelihood and frequency of bone or joint imaging was higher during the diagnosis period and similar during the follow-up period when comparing individuals with and without BM according to Approach 3 (Table 4). The likelihood and frequency of PSA tests during the diagnosis period was higher when comparing individuals with and without BM according to SEER (Table 3). Among the 1,694 patients and during either the diagnosis or follow-up periods, the likelihood of a PSA test was lower and the frequency of PSA testing was not statistically significantly different when considering Approach 3 (Table 4).
Table 4

Health services utilization among patients with SEER-based evidence of BM (M1b), stratified by presence or absence of concurrent BM according to claims-based Algorithm 3

 

M1b Sample

Concurrent BM claims algorithm 3

No concurrent BM claims algorithm 3

p-value

 

N = 1,694

N = 813

N = 881

 

(48.0%)

(52.0%)

 

 N

Col%

 N

Col%

 N

Col%

 

Post-diagnosis resource utilization (i.e., till end of follow-up)

       

 Bone mineral density (BMD) test

71

4.2

28

3.5

43

4.9

0.14

 PSA test

1,389

82.0

640

78.7

749

85.0

<0.01

 Oncologist visit

1,041

61.5

567

69.7

474

53.8

<0.01

 Nuclear medicine specialist visit

NR

NR

NR

+

NR

-

0.10

 Radiation oncologist visit

687

40.6

369

45.4

318

36.1

<0.01

 Bone biopsy

47

2.8

NR

+

NR

-

<0.01

 Bone or joint imaging

1,406

83.0

684

84.1

722

82.0

0.23

Treatment receipt (Part B)

       

 Radiation

581

34.3

315

38.8

266

30.2

<0.01

 External beam radiation therapy

553

32.6

302

37.2

251

28.5

<0.01

 Radiopharmaceutical therapy

72

4.3

45

5.5

27

3.1

0.01

 Bisphosphonates IV

593

35.0

351

43.2

242

27.5

<0.01

 Erythropoietin

352

20.8

192

23.6

160

18.2

0.01

 Opioids (moderate-severe)

379

22.4

167

20.5

212

24.1

0.08

Resource utilization during the 90-day diagnosis period

       

 PSA test

1,046

61.8

481

59.2

565

64.1

0.04

 Bone biopsy

42

2.5

NR

+

NR

-

<0.01

 Bone or joint imaging

1317

77.7

690

84.9

627

71.2

<0.01

 

Mean

S.D.

Mean

S.D.

Mean

S.D.

p-value

Post-diagnosis resource utilization (i.e., till end of follow-up)

       

 Number of BMD tests

0.04

0.22

0.04

0.19

0.05

0.24

0.11

 Number of PSA tests

8.81

10.41

8.80

10.90

8.83

9.95

0.95

 Number of bone biopsies

0.03

0.18

0.05

0.24

0.01

0.09

<0.01

 Number of bone or joint imaging

1.73

1.61

1.70

1.56

1.75

1.66

0.51

Resource utilization during the 90-day diagnosis period

       

 Number of PSA tests

0.92

0.94

0.95

1.04

0.89

0.83

0.18

 Number of bone biopsies

0.03

0.17

0.05

0.24

0.003

0.06

<0.01

 Number of bone or joint imaging

0.79

0.44

0.87

0.41

0.72

0.47

<0.01

NR, Not reported due to small sample size, per data use agreement; ‘+’ means that the column% is greater than the percentage for the full sample while ‘-‘means that the column% is smaller than the percentage for the full sample.

With the focus on improving the sensitivity of Approach 3 based on results in Table 3, we expanded the definition of Approach 3 to include situations where there were two outpatient claims during the diagnosis period for a PSA test or a bone/joint imaging test. The tests had to occur within 90 days of each other. Following this exercise, sensitivity of the expanded Approach 3 was improved: 0.581 (0.558 – 0.605) compared to 0.48 (0.456 – 0.504) for the original Approach 3. The specificity of the updated Approach 3 was reduced: 0.558 (0.527 – 0.589) compared to 0.62 (0.59 – 0.65) for the original Approach 3. Changes to the algorithm focused on specificity also can be identified and implemented.

Discussion

Evaluation of the incidence and impact of BM among cancer patients requires reliable estimation of BM. We found that there is low to moderate concordance between the SEER-based and claims-based measures of bone metastasis (BM) in a sample of men diagnosed with incident advanced disease. We conducted the analysis using data on men diagnosed with incident advanced PCa although the investigation would be relevant to any study using healthcare claims data to investigate the occurrence of BM among individuals diagnosed with advanced stage cancer. We found that inconsistency in terms of the absence of incident BM diagnosis according to the registry data and the presence of a baseline BM diagnosis according to the claims data occurred when a generous (i.e. catch-all) claims-based measure was employed. The greatest potential for missing patients with an incident diagnosis of BM according to the registry data occurred when employing a restrictive claims-based measure. Our study leveraged the availability of SEER-based and claims-based information regarding the same clinical event, i.e. the diagnosis of BM in the registry data and health care utilization that is ostensibly related to either diagnosis or treatment of BM in the Medicare claims data.

Medicare claims constitute a rich source of information for investigating treatment utilization and management over time for patients with continuous Medicare coverage. When linked with cancer registry data, the claims data provide important information regarding treatment and management following the cancer diagnosis. The potential benefits of claims data have to be considered in the context of some of the limitations, including the limited ability to confirm the presence of clinically diagnosed conditions. In this paper, we focused on the diagnosis of BM among elderly men with PCa given the implications of a BM diagnosis on patient quality of life [19], prognosis [6, 19, 20], and treatment costs [4]. When the BM diagnosis occurs concurrently with the PCa diagnosis, post-diagnosis cancer care shifts dramatically to an increased focus on bone health, pain management, and quality of life. The BM diagnosis can also occur after the initial diagnosis of PCa, with often severe implications for the patient’s health. Thus, it would be important to be able to reliably identify the population of patients with BM using generalizable data such as SEER-Medicare.

The SEER-Medicare cohort included men diagnosed with PCa from 2005 to 2007, providing the opportunity to investigate the concordance between the data regarding an incident BM diagnosis supplied by the cancer registries and information from the claims data regarding BM-related health care utilization around the diagnosis period. We excluded the 2004 cohort since that was the first year that information regarding a BM diagnosis was available from the SEER registry. Approach 1 was created based on the rationale that coding for BM on a health care claim would occur only when the patient had a diagnosis of BM. Approach 3 was created based on the rationale that: 1) in the inpatient setting, a hospitalized individual with a BM diagnosis may not necessarily be hospitalized as a result of their specific BM diagnosis, and therefore the diagnosis code of BM could appear in any position within the diagnosis fields; and 2) in the outpatient setting, a claim for a service that could be used to diagnose (or rule out) BM may be more useful if at least two claims were required to be more certain that BM was present.

None of the approaches in Table 2 was uniformly superior and given the focus on identifying the concordance between available measures of bone metastasis, the next step with respect to the development of reliable claims-based measures would be to provide guidance on the avenues for improving their reliability. Based on information in Table 3 regarding utilization during the diagnosis period, the frequency of PSA testing and the frequency of bone/joint imaging was higher among individuals with incident BM diagnosis according to the SEER registry data compared to individuals who were not identified in SEER as having BM. The higher testing frequency may reflect more intense follow-up schedules involving specific tests after a diagnosis of BM compared to patients who do not have a BM diagnosis. The results from this exercise indicated that it is possible to improve the sensitivity of claims-based measures. Results also suggest that the informative measures that emerge when analyzing data within a retrospective study design will not be limited to ‘predictive’ variables and that researchers may also draw inference from utilization patterns that occur following the BM diagnosis.

There are some limitations that also need to be considered. There has been no validation of the SEER registry M1b measure and so its measurement properties are not fully understood. We excluded registry data on M1b for the 2004 cohort year however some inaccuracies in M1b coding could still be present in subsequent years. Reliance on ICD 9 diagnosis coding for BM could be problematic when examining outpatient claims for diagnostic tests and procedures. Claims associated with services intended to rule out BM should not include the 198.5 code on the claim since the BM diagnosis is not established. A two-step approach for including diagnostic tests/procedures based on diagnosis codes may be: 1) examine all claims regardless of whether or not they have a BM ICD 9 code; 2) include only those diagnostic claims that are followed (e.g. within 90 days) by a claim of 198.5.

The comparison undertaken in this study is instructive for two important reasons: 1) as noted in the introductory text, claims-based measures are already in use by researchers to investigate the clinical and economic burden of BM across various disease sites and will remain a source for population-based, real-world evidence regarding prevalence, utilization, and outcomes associated with metastasis to the bone; 2) the linked cancer registry data provide unique clinical, cancer-specific information and are generally considered to be more reliable than claims data for confirming clinical diagnoses (e.g., AJCC M1 staging information available in SEER compared with ICD 9 codes for distant metastasis). However, information regarding disease progression and health utilization (e.g., treatment, physician visits, hospice use) is not available in registry data thus claims data will remain the source of information on utilization among incident and prevalent BM cases across cancer sites including prostate cancer, lung cancer, and breast cancer. From a public health standpoint focused on improving health outcomes for men and women with advanced cancer, it will be important to develop validated measures of a BM diagnosis using claims-based data.

Conclusion

We identified low to moderate concordance between the Medicare claims anchoring on codes used for diagnosing bone metastasis and the SEER registry data that is indicative of incident diagnosis of bone metastasis. Researchers utilizing the SEER or linked SEER datasets to investigate bone metastasis should exercise caution given the low agreement between the two sources of information regarding an incident diagnosis of bone metastasis. Until further research provides a validated claims-based approach to identifying BM, it is prudent to focus on individuals with metastatic disease and not seek to subset the population further based on metastasis to the bone. Claims-based approaches should be validated against chart data to maximize their potential for population-based analyses.

Abbreviations

AJCC: 

American joint committee on cancer

BM: 

Bone metastasis

CCI: 

Charlson Comorbidity Index

CS: 

Collaborative stage

HMO: 

Health Maintenance Organization

ICD 9 CM: 

International classification of diseases, 9th revision clinical modification

MEDPAR: 

Medicare provider analysis and review

NCI: 

National Cancer Institute

PCa: 

Prostate cancer

PPV: 

Positive predictive value

PSA: 

Prostate-specific antigen

SEER: 

Surveillance, epidemiology, and end results

TNM: 

Tumor, node, metastasis.

Declarations

Acknowledgement

The authors thank Kaloyan Bikov for feedback received and the staff from Pharmaceutical Research Computing for programming assistance on the primary datasets.

This study used the linked SEER-Medicare database. The interpretation and reporting of these data are the sole responsibility of the authors. The authors acknowledge the efforts of the Applied Research Program, NCI; the Office of Research, Development and Information, CMS; Information Management Services, Inc.; and the Surveillance, Epidemiology, and End Results (SEER) Program tumor registries in the creation of the SEER-Medicare database.

The collection of the California cancer incidence data used in this study was supported by the California Department of Public Health as part of the statewide cancer reporting program mandated by California Health and Safety Code Section 103885; the National Cancer Institute’s Surveillance, Epidemiology and End Results Program under contract N01-PC-35136 awarded to the Northern California Cancer Center, contract N01-PC-35139 awarded to the University of Southern California, and contract N02-PC-15105 awarded to the Public Health Institute; and the Centers for Disease Control and Prevention’s National Program of Cancer Registries, under agreement #U55/CCR921930-02 awarded to the Public Health Institute. The ideas and opinions expressed herein are those of the author(s) and endorsement by the State of California, Department of Public Health the National Cancer Institute, and the Centers for Disease Control and Prevention or their Contractors and Subcontractors is not intended nor should be inferred. The authors acknowledge the efforts of the Applied Research Program, NCI; the Office of Research, Development and Information, CMS; Information Management Services (IMS), Inc.; and the Surveillance, Epidemiology, and End Results (SEER) Program tumor registries in the creation of the SEER-Medicare database.

Funding sources

The study is funded by Bayer Healthcare Pharmaceuticals. AH’s role was supported in part by the Department of Veterans Affairs Merit Review Award.

Authors’ Affiliations

(1)
Pharmaceutical Health Services Research Department, University of Maryland School of Pharmacy
(2)
Department of Medicine, University of Maryland School of Medicine
(3)
Baltimore Veterans Affairs Medical Center
(4)
Bayer Healthcare Pharmaceuticals

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  21. Pre-publication history

    1. The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2288/14/1/prepub

Copyright

© Onukwugha et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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