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Table 4 Comparison of Analytic Approaches Using Data on Delirium and Interleukin-6 (IL-6)

From: Methodologic considerations in the design and analysis of nested case-control studies: association between cytokines and postoperative delirium

 

Number of Subjects

PREOP

PACU

POD2

(a) Matched Analysis of Delirium as the Outcome vs IL-6 as the Outcome

Matched Analysisa

 Delirium as the Outcome

78 (39:39)

   

 Beta (SE)

 

0.00745 (0.0112)

0.00321 (0.00327)

0.0154 (0.0054)

  P-value

 

0.508

0.326

0.005

 Odds Ratio (95% CI)

 

1.01 (0.99–1.03)

1.00 (0.99–1.01)

1.02 (1.01–1.03)

Matched Analysisb

 IL-6 as the Outcome

78 (39:39)

   

 MPD

 

1.11

9.13

50.44

  P-value

 

0.475

0.123

0.005

(b) Matched Analysis Using Observed IL-6 vs. Unmatched Analysis Using Simulated IL-6

Unmatched Analysis

 Simulated IL-6c

192 (49:143)

   

 Beta (SE)

 

-0.0385 (0.0322)

0.00323 (0.002)

0.0176 (0.004)

  P-value

 

0.231

0.105

0.0001

 Odds Ratio (95% CI)

 

0.96 (0.90–1.03)

1.00 (0.99–1.01)

1.02 (1.01–1.03)

Matched Analysis

 Observed IL-6d

78 (39:39)

   

 Beta (SE)

 

0.00745 (0.0112)

0.00321 (0.00327)

0.0154 (0.0054)

  P-value

 

0.508

0.326

0.005

 Odds Ratio (95% CI)

 

1.01 (0.99–1.03)

1.00 (0.99–1.01)

1.02 (1.01–1.03)

  1. aThe coefficients (Beta and SE), p-values, and odds ratios came from the conditional logistic regression where delirium case was the outcome, and IL-6 the independent variable
  2. bThe MPD (median paired differences) is the median of the paired differences (concentration level of IL-6 from the delirium case minus that of the control) within each time period. The p-values came from the nonparametric signed rank test
  3. PREOP preoperative, PACU post-anesthesia care unit, POD2 postoperative day 2, SE standard error, CI confidence interval
  4. cThe coefficients (Beta, SE), p-values, and odds ratios came from the unconditional multivariable logistic regression with delirium case as the outcome, and the six match factors as independent variables
  5. dThe coefficients (Beta, SE), p-values, and odds ratios came from the conditional logistic regression where delirium case is the dependent variable, and IL-6 the independent variable
  6. PREOP preoperative, PACU post-anesthesia care unit, POD2 postoperative day 2, SE standard error, CI confidence interval