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Table 4 Linkage Weight Calculator

From: Linkage of primary care prescribing records and pharmacy dispensing Records in the Salford Lung Study: application in asthma

Factor

Criteria

Points

Factor Range

% of candidates

% of matches

Brand Name *

Both records had non-missing, and distinct, brand names

0

0–20

6.3%

2.8%

One or both of the records had a missing brand name

10

0%

0%

Both records had non-missing, and matching, brand names

20

93.7%

97.2%

(Modified) Dose Strength

Both records had non-missing, and distinct, dose strengths

0

0–35

4.8%

0%

One or both of the records had a missing dose strength

10

18.1%

9.0%

Both records had non-missing, and matching, dose strengths

35

77.2%

91.0%

(Modified) Medication Quantity

Both records had non-missing, and distinct, primary and alias dose quantities

0

0–35

4.2%

0%

One or both of the records had a missing primary quantity value, indicating that no value was observed or could be imputed

10

9.8%

< 0.1%

Both records had non-missing, and distinct, primary dose quantities, but the alias of one record matched to the primary of the other

15

4.9%

1.5%

Both records had non-missing, and matching, primary dose quantities

35

81.1%

98.5%

Date difference

Dispensing occurred more than one month after prescription (but less than six months)

0

0–10

67.2%

1.3%

Dispensing occurred within one month of prescription

10

32.8%

98.7%

  1. * If a generic medication was used, the brand name was listed as ‘generic’