Fig. 2 . Calculation of pseudosensitivity and PPV.

A true positive (a) was a case identified by a case-finding algorithm and by medical record review and a false positive (b) was a case identified by a case-finding algorithm but not by medical record review. A false negative (c) was a case identified by medical record review but not by a case-finding algorithm and a true negative (d) was a case that was not identified by medical record review or by a case-finding algorithm. PPV was calculated as a/(a + b), and pseudosensitivity was calculated as a/(a + c) and was termed “sensitivity”.

NPV: negative predictive value, PPV: positive predictive value.