Before recommending the skin-test use at national level in Guatemala of an antigen prepared from Leishmania major (a Leishmania species not found in the New World), we conducted a study in 100 Guatemalans to determine its sensitivity and specificity. The antigen consisted of 0.1 mL of a solution that contained 5 X lo6 promastigotes of L. major (MRHOIIRI75IVAX).
Positive leishmanin skin test (LST) reactions at 48 h were observed in 16 (80%) of 20 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 healthy 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 specificity of 100%. There were no statistically significant differences in ethnic group, age, duration of the lesion, lesion size or Leishmania species between the 34 persons with true positive reactions. Even though it will be necessary to test this antigen on a larger number ofpatients, these preliminary results show that this antigen is specific and reasonably sensitive in identifying current or past CL and that it is a reasonable choice for epidemiological studies on CL in Guatemala.