Diagnostic value of a single, pre-treatment Widal test in suspected enteric fever cases in the Philippines.

101 patients with a clinical suspicion of typhoid or paratyphoid (enteric) fever admitted to San Lazaro Hospital, Manila, Philippines, were studied by bacteriological culture of blood, rectal swab, urine and duodenal string capsule; 35 also had bacteriological culture of bone marrow aspirate. 44 of the patients were culture-confirmed as having enteric fever; the remainder were classified as non-enteric fever cases. Analysis of the pretreatment Widal agglutination titres of all patients revealed that using as a diagnostic criterion an antibody titre of greater than or equal to 1:80 to the O antigen of Salmonella typhi yielded a test specificity of 100%, although the corresponding sensitivity was only 64%. The sensitivity of the test could be increased to 80% by using different cut-off values for titres to flagellar antigens, but this concomitantly decreased the test specificity from 100 to 82%. The data indicate that a single pretreatment Widal test in suspected enteric fever cases is of definite diagnostic value, but that the results must be interpreted with caution and foreknowledge of the test's shortcomings and limitations.