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Table 2 Raw data, sensitivity, specificity and positive predictive value and negative predictive value for the four different delays in pharmacy pick-ups

From: Identification of losses to follow-up in a community-based antiretroviral therapy clinic in South Africa using a computerized pharmacy tracking system

Delays of

pharmacy

pick-ups,

weeks*

a

b

c

d

Sensitivity

%(95% CI)

Specificity

%(95% CI)

PPV

% (95% CI)

NPV

% (95% CI)

≥6

85

475

0

1988

100.0 (95.8-100.0)

80.7 (79.1-82.3)

15.2 (12.2-18.2)

100.0 (99.8 -100.0)

≥12

85

109

0

2354

100.0 (95.8-100.0)

95.6 (94.7-96.4)

43.8 (36.8-50.9)

100.0 (99.8-100.0)

≥18

53

64

32

2399

62.4 (51.2-72.6)

97.4 (96.7-98.0)

45.3 (36.1-54.5)

98.7 (98.1-99.1)

≥24

40

40

45

2423

47.1 (36.1-58.2)

98.4 (97.8-98.8)

50.0 (38.8-61.2)

98.2 (97.6-98.7)

  1. *Pharmacy delays detected by iDART were compared to true LTFU status; a, true positives; b, false positives; c, false negatives; d, true negatives; PPV, positive predictive value; NPV, negative predictive value; %, percentage and CI, confidence intervals