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Published on: March 22, 2012
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A Multicenter evaluation of leprosy rapid test Fast ML Flow Hanseníase in Brazil
Djairo Pastor Saavedra1,2, Maurício Lisboa Nobre3, Rafael Alves Guimarães4
1Rapid Test Development and Production Laboratory, Institute of Tropical Pathology and Public Health, Federal University of Goiás, LDPTR/IPTSP/UFG), Goiânia, GO, 74605-050, Brazil.
Summary
The Fast ML Flow Hanseníase (MLFH) test shows higher leprosy detection rates in Brazil compared to other methods. However, its modified criteria may lower specificity when screening asymptomatic contacts.
Area of Science:
- Medical Diagnostics
- Infectious Diseases
- Public Health
Background:
- Leprosy diagnosis is primarily clinical, posing a public health challenge.
- The Brazilian public health system (SUS) integrated the leprosy-specific IgM anti-PGL-I rapid test, Fast ML Flow Hanseníase (MLFH), for leprosy contact surveillance and diagnosis.
- Anti-PGL-I antibody levels are known to correlate with leprosy bacterial load.
Purpose of the Study:
- To evaluate the performance of the MLFH test in confirmed leprosy cases across four Brazilian reference centers.
- To compare MLFH results with established diagnostic methods like anti-PGL-I ELISA and bacilloscopy.
- To assess MLFH performance across different leprosy classifications, including indeterminate, pure neuritic, and Ridley Jopling categories.
Main Methods:
- A multicenter study involving 158 leprosy patients (95 multibacillary/MB, 63 paucibacillary/PB).
- Comparison of MLFH results against anti-PGL-I ELISA and bacilloscopy (BI).
- Evaluation of MLFH repeatability, inter-center, and inter-operator reproducibility using 20 distributed leprosy samples.
Main Results:
- MLFH demonstrated higher seropositivity (84.8%) than ELISA (60.8%) and bacilloscopy (50.6%), with moderate and fair agreement, respectively.
- Excellent agreement (ICC: 0.954) and high repeatability (95.57%) were observed for MLFH visual intensity readings.
- Statistically significant differences in positivity were noted between MLFH, ELISA, and bacilloscopy in tuberculoid (TT), borderline-tuberculoid (BT), and indeterminate (I) leprosy forms.
Conclusions:
- The revised MLFH criteria (including faint lines) increased test sensitivity, particularly for paucibacillary leprosy.
- This modification leads to higher seropositivity, especially in paucibacillary cases, which are typically weak antibody producers.
- The enhanced sensitivity with the modified criterion may compromise specificity when screening asymptomatic contacts in endemic areas, as anti-PGL-I positivity alone doesn't confirm active disease.
