Tel: 01432 277707
Director: Dr Venkat Sivaprakasam
The Health Protection Agency, Leptospira Reference Unit (LRU), provides a national reference facility for HPA and NHS Medical Microbiology laboratories.
The unit offers a range of investigations, including serological diagnosis of human leptospirosis and isolation of leptospires from clinical material. The unit offers an advisory service on the investigation of patients for leptospirosis, the type and relevance of tests, their timing, and on the interpretation of results. Advice on treatment is also available.
See here for Samples and Testing Policy.
If you need advice on the clinical interpretation of results, the Unit Director may be reached on: 01432 277707.
For advice on the types of samples required, or on the timing of sampling, or on all technical matters, please contact the Biomedical Staff on: 01432 277707.
Please telephone the LRU to arrange a request for urgent Leptospira serology.
Where possible, please use the LRU request form when submitting samples and ensure that all sections have been completed. Please indicate clearly the department and hospital from which the request has been made to ensure that results can be returned; a contact telephone number is advisable.
NB. Specimens sent to a clinical laboratory for diagnosis must comply with the regulations laid down in the Post Office Regulations governing the transport of pathological specimens. http://www.toxlab.co.uk/curregs.htm and http://www.ukncc.co.uk/html/Information/Postal%20Regulations.htm
Serology: A minimum volume of 250µl of serum is required. Initial samples should be taken 5 - 7 days after the onset of symptoms.
For isolation of leptospires (where appropriate)
Blood cultures: Ideally, blood cultures should be taken within the first 5 days after the onset of symptoms and before the administration of antibiotics and sent directly to the LRU. Since the optimal incubation temperature for leptospires is 29 - 30°C, retaining blood cultures at room temperature until despatch to the LRU will be the most advantageous for the recovery of leptospires. Blood should be taken into blood culture (BacT/ALERT, BacTec) or mycobacterial blood culture (BacT/ALERT MB) AEROBIC bottles, or an aliquot from one of the above. Hold at 29°C or at room temperature until dispatched to the LRU.
Fixed or unfixed post mortem tissue is only accepted after prior discussion with consultant staff.
Urine samples are not suitable for the isolation of leptospires due to the presence of other contaminating bacteria and the poor viability of leptospires in urine.
Two tests are offered by the LRU for the serological diagnosis of leptospirosis. An 'in house' ELISA is used to screen all sera, with positive results confirmed by the standard reference method, the Microscopic Agglutination Test (MAT).
A. Leptospira IgM ELISA
Leptospira IgM antibodies may be detectable 5 days after the onset of symptoms, but not usually before this. In cases where antibiotic treatment has been initiated, this period may be increased. Once a patient has produced IgM antibodies, they can remain detectable for months, or even years. IgG antibodies may only be detected for a short period, if at all.
An IgM titre of 1:320 is considered suggestive of leptospiral infection and further samples will be required to confirm a diagnosis in conjunction with the MAT.
Low IgM titres of 1:80 to 1:160 may be indicative of early infection, or with possible cross-reaction with other conditions, e.g. EBV or Hepatitis A.
Further samples will be required to confirm results.
The IgM ELISA test has a 90% sensitivity and 93% specificity (J Clin Pathol, 2001; 54: 25-30).
B. Microscopic Agglutination Test (MAT)
The MAT may be positive from about day 10 after onset of symptoms. To determine the presumptive infecting serogroup in acute leptospiral infection it may be necessary to examine samples taken over a period of several weeks.
Routine serological analyses are undertaken in batches on a twice weekly basis. Results will be issued at the earliest opportunity, usually 7 working days.
There is little point in testing fresh surface water for leptospira. The test only detects leptospira in a small volume of the water and at a single point in time. It is also expensive and lengthy (6 weeks). A different area of the surface water body could have leptospira present, or there could be leptospires present shortly after the sample was taken. Leptospires are sensitive to chlorination of domestic water supplies.
The simple precautions outlined in the Q&A should minimise the risk to water users.
Last reviewed: 5 July 2012