SENSITIVITY AND SPECIFICITY OF DIAGNOSTIC-TESTS IN ACUTE MAXILLARY SINUSITIS DETERMINED BY MAXIMUM-LIKELIHOOD IN THE ABSENCE OF AN EXTERNALSTANDARD

This study shows how to obtain maximum likelihood estimates of test se nsitivities and specificities in case of lack of an external standard, using the Expectation Maximisation (EM) algorithm. This method is use d to compare four diagnostic tests in patients suspected of acute maxi llary sinusitis. Data were analyzed from published studies. Antral asp iration is the test with the highest diagnostic value. The diagnostic value of a positive clinical examination (according to explicit criter ia) and of a positive radiograph or ultrasound are comparable. A negat ive radiograph is of more diagnostic value than a negative clinical ex amination or ultrasound. The width of the confidence intervals may be too small, due to model deviations which may give incorrect standard e rrors. However, the estimated likelihood ratios adequately reflect the relative value of the diagnostic tests considered, even when the assu mption of independence is dropped.