New patient-oriented diagnostic test characteristics analogous to the likelihood ratios conveyed information on trustworthiness.
OBJECTIVE
Suggesting patient-oriented ratio measures of diagnostic tests analogous to the likelihood ratios.


METHODS
Algebraic equation based on Bayes' theorem.


RESULTS
Two new measures are suggested: the positive predictive ratio (PPR), relating the positive predictive value (PPV) to the false negative rate in the patient population, and the negative predictive ratio (NPR), relating the negative predictive value (NPV) to the false positive rate in the patient population. The new measures are analogous to likelihood ratios. These measures are calculable from the familiar 2x2 table in a selected study population or in a target (general) population. Examples are given, using published data.


CONCLUSIONS
PPR adds to the information given by the PPV, and NPR adds to the information given by the NPV. PPR and NPR may be more appropriate in the clinical setting than likelihood ratios.
Linn
Shai
S
School of Public Health, Faculty of Welfare and Health Studies, Hafa University, Abba Khoushy Road, Haifa, Israel. slinn@univ.haifa.ac.il
D001499:Bayes Theorem; D016001:Confidence Intervals; D005080:Exercise Test / Q000379:methods; D006801:Humans; D016013:Likelihood Functions; D008433:Mathematics; D015233:Models, Statistical; D010361:Patients; D011237:Predictive Value of Tests; D009626:Terminology as Topic; D016216:Ultrasonography, Prenatal / Q000379:methods