Table 2:

Test characteristics of screening to predict methicillin resistance in clinical isolates of Staphylococcus aureus, stratified by time from screening swab to isolate collection

CharacteristicOverallImmediate*Recent†Remote‡
True positive, no.50201713
True negative, no.42812720398
False positive, no.3012
False negative, no.2921215
Sensitivity, % (95% CI)63 (52–74)91 (71–99)59 (39–77)46 (28–66)
Specificity, % (95% CI)99 (98–100)100 (97–100)100 (97–100)98 (93–100)
Positive likelihood ratio (95% CI)91 (29–284)–§120 (17–865)29 (7–120)
Negative likelihood ratio (95% CI)0.37 (0.28–0.49)0.09 (0.01–0.30)0.42 (0.27–0.64)0.42 (0.27–0.65)
Positive predictive value, % (95% CI)94 (84–99)100 (83–100)94 (73–100)87 (60–98)
Negative predictive value, % (95% CI)94 (91–96)98 (95–100)94 (90–97)87 (79–92)

  • CI = confidence interval.

  • ↵* Swab obtained within 48 hours before isolate collection.

  • ↵† Swab obtained between 48 hours and 14 days before isolate collection.

  • ↵‡ Swab obtained more than 14 days before isolate collection.

  • ↵§ Test characteristics could not be calculated owing to high specificity values.