Evaluation of agreement between tests for the diagnosis of leprosy

Abstract

Introduction:

Leprosy is a chronic infectious disease caused by the intracellular parasite Mycobacterium leprae. The diagnosis is essentially clinical, based on symptoms, skin exam, peripheral nerves and epidemiological history. Laboratory tests are carried out to complement the result of clinical diagnosis, or even serving as a confirmatory method.

Objective:

To investigate the positivity and agreement between skin smear, enzyme-linked immunosorbent assay (ELISA) with synthetic antigen ND-O-BSA, ML Flow test and polymerase chain reaction (PCR) for detection of Mycobacterium leprae in new cases of leprosy.

Methods:

We conducted a case series study assessing a convenience sample of 39 new cases of leprosy and a control group of 18 household contacts in Belém (PA) and in Igarapé-Açu (PA) from March 2014 to September 2015.

Results:

The agreement between ELISA, ML Flow and PCR tests combinations showed slight to absent reproducibility (Kappa ≤ 0.24). The results showed greater sensitivity in PCR assay, with higher positivity in multibacillary cases. The ELISA test showed low positivity, even in multibacillary cases, resulting in no reaction to paucibacillary cases and household contacts.

Conclusion:

The high sensitivity of PCR decreases the agreement with other tests.