Laboratory diagnostic tools for leprosy

Leprosy Mailing List –  March 15th, 2011

Ref:    Laboratory diagnostic tools for leprosy. 

From: Das P K, Amsterdam, The Netherlands

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Dear Leon Gilead,

Thank you for your message dated LML March 8^th, 2011.

Lepromin reagents are still produced by Dr. Esther at the Institute Lauro Souza Lima, inBauru , Brazil .  Among the laboratory tests still the IgM titre to PGL-1 (high bacilli laden forms of leprosy only) is the golden standard. 

In addition, IgG and IgM to gel purified 29/33 KDa doublet and IgG and IgM titre to gel purified 65KDa antigen will diagnose LL /BL and TT/BT cases respectively (kindly, see the publication J. Clin Microbiol by Das PK et al 1990). 

One can, therefore also perform ELISA using gel purified 29Kd/33Kd doublet and 64-65 KD singlet antigens, in parallel to lepromin test and IgM -PGL-1 by ELISA.  These antigens are prepared easily by first electrophoresing the BCG homoheganates in reducing SDS gel;followed by cutting out the bands of 29/33KD doublet and /^4-65 KD singlet and then eluted with distilled water.  By combining the ELISA measurement of IG/IGM titre with 29/33KD doublet and 64-65KD singlet with the western blotting pattern showing 29/33KD doublet bands and strong band of 64-65 singlet band will confirm lepromatous side (LL/BL) and diagnose BT/TT of the spectrum respectively.  In this latter test, true BB cannot be diagnosed.

Further, serum cytokine and chemokine profiling is advisable for monitoring the patients (see the publications by de Silva E et al, Lyer et al etc.).  Recently IDEAL group strongly advise cell based assay like that of quantiferon for TB also for leprosy using post genomic antigens.

A combination of serum anti-PGL-1 Ab test positive plus lepromin skin test negative will be consistent with diagnosis of leprosy on the lepromatous side of the spectrum.  While a combination of serum anti-PGL-1 Ab test negative plus lepromin skin test positive will be consistent with diagnosis of leprosy at the tuberculoid side of the spectrum.  So far this is the best laboratory diagnostic tool that we have got.  It matches with the clinical diagnosis and is robust enough to diagnose >90% of the patients.

Hope that this information is useful.

Pranab

Table. Laboratory diagnostic tools in leprosy: anti-PGL-1 Ab and lepromin tests
serum anti-PGL-1 Ab test positive	+	lepromin skin test negative	consistent with diagnosis of	leprosy at the lepromatous side of the spectrum
serum anti-PGL-1 Ab test negative	+	lepromin skin test positive	consistent with diagnosis of	leprosy at the tuberculoid side of the spectrum