Table 1.

Advantages and Disadvantages of Diagnostic Assays Available for Leptospirosis.

Assay	Specimen Type	Target	Comments
Darkfield microscopy	Urine	Leptospira organisms	Low sensitivity and specificity. Requires considerable technical expertise to interpret correctly.
Culture	Whole blood, urine	Leptospires	Special media required. Although sensitivity has historically been considered low and prolonged incubation times have been required, recent improvements in media have been associated with increased yields and shorter incubation times.
Microscopic agglutination test	Serum	Antibodies against various leptospiral serovars	False negatives can occur early in the course of illness or with immunosuppression, or when panels are used with limited numbers of serovars. False positives can occur with a history of vaccination in animals or with previous exposure. Paired titers performed at the same laboratory generally required for diagnosis. Inter-laboratory variation in results may occur.
Rapid diagnostic chromatographic or ELISA based tests	Serum or plasma	IgM or IgG against Leptospira	False negatives can occur early in the course of illness or with immunosuppression. False positives can occur with a history of vaccination in animals or with previous exposure. Weak positive results can be difficult to read. No information in infecting serogroup.
Histopathology	Kidney tissue collected via biopsy or necropsy	Leptospires	Organisms may be visualized with silver stains, immunohistochemistry, or fluorescence in situ hybridization. Antimicrobial therapy may lead to false-negative results.
Nucleic acid amplification tests	Blood, urine, CSF, tissue specimens	Leptospira DNA	Sensitivity and specificity unclear and may vary between assays offered by different laboratories. Antimicrobial therapy may lead to negative results. A positive result from a urine specimen may not have etiologic predictive value because of the potential for subclinical carriage.