Evaluation of a standardized leishmanin skin test in Guatemala

Before recommending the skin-test use at national level in Guatemala of an antigen prepared from Leishmania major (a Leishmania species not found in t he New World), we conducted a study in 100 Guatemalans to determine its sen sitivity and specificity. The antigen consisted of 0.1 mL of a solution tha t contained 5 X 10(6) promastigotes of L. major (MRHO/IR/75/VAX). Positive leishmanin skin test (LST) reactions at 48 h were observed in 16 (80%) of 2 0 patients with proven active cutaneous leishmaniasis (CL), 18 (90%) of 20 with previously treated proven CL, and in 18 (90%) of 20 with a history and compatible scar of previously suspected but unconfirmed CL. None of 20 hea lthy controls or 20 patients with skin lesions due to causes other than CL had positive reactions to the LST, giving a sensitivity of 85% and specific ity of 100%. There were no statistically significant differences in ethnic group, age, duration of the lesion, lesion size or Leishmania species betwe en the 34 persons with true positive reactions. Even though it will be nece ssary to test this antigen on a larger number of patients, these preliminar y results show that this antigen is specific and reasonably sensitive in id entifying current or past CL and that it is a reasonable choice for epidemi ological studies on CL in Guatemala.