Diagnosis of symptomatic kala-azar by polymerase chain reaction using patient's blood.

Background: Detection of Leishmania parasite in patients by classical methods at the early stage of infection is limited. Several studies have shown that polymerase chain reaction (PCR) is more effective for the diagnosis of visceral Leishmaniasis (VL) in clinical samples. The purpose of this study was to develop a simple, specific and sensitive PCR-based assay for detecting VL caused by any species of the genus Leishmania.

Material/methods: We examined blood samples from twenty suspected kala-azar patients by polymerase chain reaction (PCR) using Leishmania specific primers. The results of the PCR-based procedure were compared with those of the Leishman-Donovan (LD) body test, immunodiffusion assay (IDA), and direct agglutination test (DAT).

Results: Out of the twenty samples, only five were found to be positive using all four tests. However, twelve samples were positive using the PCR assay, and among these only ten samples were found to be positive by LD body test of bone marrow smears. The results clearly indicated that, unlike the LD body test routinely used for diagnosis of kala-azar, the PCR assay is 100% sensitive.

Conclusions: This method is very useful for primary screening of blood samples of patients suffering from kala-azar-like symptoms, especially in endemic areas.