The myriad spectrum of leptospirosis makes it difficult to confirm a diagnosis without adequate laboratory facility. Ideally a microbiological confirmation should be sought for, however, it is not always possible, as many laboratories do not have the necessary expertise. In such situations simple clinical, epidemiological and biochemical findings can be of great help in the diagnosis of infection.
After infection, leptospires are present in the blood until they are cleared after 4 to 7 days following the production of anti–Leptospira antibodies, initially mainly of the IgM class. The laboratory diagnosis of leptospirosis mainly relies on the detection of these anti–Leptospira antibodies in patients’ serum. Several methods are available for this purpose:
- The microscopic agglutination test (MAT) is the cornerstone of the serodiagnosis of leptospirosis, because this assay has a high sensitivity and allows for the detection of group–specific antibodies.
- Enzyme–Linked ImmunoSorbent Assay (ELISA) or indirect fluorescent antibody tests (IFAT) have a capacity to detect with a high sensitivity specific IgM antibodies as a sign of current or recent leptospirosis.
- PCR proved to be a successful method to detect Leptospira DNA in serum and even better in urine in the first week of infection. It can also be used to detect Leptospira DNA in tissues for post–mortem diagnosis, which are useful when conventional methods like culture fail.
- New Lepto dipstick test is also available.