Acıbadem Üniversitesi Sağlık Bilimleri Dergisi 2014 , Vol 5, Issue 2
Using Diagnostic Test's Results In Clinical Desicion Making Process
Figen Demir
Acıbadem Üniversitesi Tıp Fakültesi Halk Sağlığı Anabilim Dalı, İstanbul, Türkiye Diagnostic tests' ability to detect a person having disease or exclude a person without disease, is described by terms such as sensitivity, specificity, positive predictive value and negative predictive value. Sensitivity and specificity are caharacteristics of diagnostic test but cannot be used to estimate the probability of disease in an individual patient. Positive and negative predictive values can be used to estimate the propability of disease but it is not easy to translate their results to individual patients. For this purpose combination of likelihood ratios and pre-test propability are used. Positive and negative likelihood ratios are clinically, more useful and practical way to have immediate clinical relevance than sensitivity or specificity. They allow the clinician to estimate the probability of disease for any individual patient and provide a summary of how many times more (or less) likely patients with a disease to have a particular result than patients without the disease. Likelihood ratios can be used together with pretest probability of disease to estimate an individual's post-test probability of disease. Nomogram is a tool which, allows to combine the likelihood ratio of a test with a patient's pre-test probability (prevelance or clinician's estimation) of disease to estimate post-test probability. Keywords : diagnostic tests, likelihood ratio, nomogram