Task shifting in primary eye care: how sensitive and specific are common signs and symptoms to predict conditions requiring referral to specialist eye personnel?

Table 4 Sensitivity, specificity and predictive value for two other referral criteria

	Right eyes
Referral Criteria	ST	NST	Total	Sensitivity	Specificity	PPV	NPV
VA<6/18 or pain Neither of above Total	413 141 554	293 450 743	706 591 1297	74. 5	60. 5	58.5	76.1
VA<6/18 or pain or red eye None of above Total	448 106 554	348 395 743	796 501 1297	80.8	53.2	56.3	78.8

Row and column totals are in italics. Data are missing for some eyes. PPV = predictive value of a positive test (abnormal sign). NPV = predictive value of a negative test (absence of the abnormal sign).

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