An evaluation of three commercial kits for use as screening methods for the detection of leptospiral antibodies in the UK.
OBJECTIVE
To compare three commercial screening tests--the PanBio leptospiral IgM enzyme linked immunosorbent assay (ELISA), the Biolisa leptospiral IgM ELISA, and the indirect haemagglutination assay (IHA)--with the microscopic agglutination test (MAT) and two "in house" ELISAs--urease and horseradish peroxidase (HRP)--for the detection of leptospiral antibodies in a local UK and Eire population.


METHODS
Two hundred sera submitted for a differential diagnosis of leptospirosis were tested by all methods. A further 142 sera from patients with antibodies to toxoplasma, Epstein-Barr virus (EBV), hepatitis A virus, rheumatoid factor, Borrelia burgdorferi, Mycoplasma pneumoniae, syphilis, cytomegalovirus, and Q fever were tested for crossreactivity.


RESULTS
Compared with the MAT, sensitivity and specificity were found to be: PanBio, 90%/94%; Biolisa with sorbent, 100%/85%; and IHA, 54%/95%. Seven of 200 trial sera gave false negative results with PanBio; 14 of 200 trial sera gave false positive results with Biolisa with sorbent, as did a further 25 of the 142 sera tested for potential crossreactivity. Two of 142 sera gave crossreactions with PanBio and IHA (one each).


CONCLUSIONS
The degree of false positivity seen with the Biolisa suggests that the recommended positive value of > or = 26 Eu/ml should be reassessed using pools of sera from local populations. When the cut off value was reassessed, using a value of > or = 40 Eu/ml, a sensitivity and specificity of 96% and 94%, respectively, was achieved. Even the modified Biolisa appears to be over sensitive and to show a high degree of non-specificity. The IHA, although specific (95%), lacked sensitivity in this study. The PanBio appeared to be the most suitable as a screening test for leptospiral IgM in the UK, although it would be advisable for all positive test results to be confirmed by a different enzyme immunoassay and the MAT.
PHLS Leptospira Reference Unit/WHO/FAO Collaborating Centre for Research on Leptospirosis, County Hospital, Hereford HR1 2ER, UK. wendy.zochowski@talk21.com
W J
WJ
Zochowski
M F
MF
Palmer
T J
TJ
Coleman
D000907:Antibodies, Bacterial / Q000097:blood*; D003429:Cross Reactions; D003951:Diagnostic Errors; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006386:Hemagglutination Tests; D006801:Humans; D007919:Leptospira / Q000276:immunology*; D007922:Leptospirosis / Q000175:diagnosis*; D008403:Mass Screening / Q000379:methods*; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D006113:United Kingdom
D000907:Antibodies, Bacterial; D011933:Reagent Kits, Diagnostic