RDT demonstration video

Rapid rK39 antigen-based tests (RDTs) are based on the antigen rK39, a recombinant product of a 39 amino acid antigen encoded by a kinesin-like gene of the L. donovani complex. Originally an ELISA method, it has been adapted to a rapid strip test for use in basic field conditions and is now very widely used in VL endemic countries.

The RDTs are available from several manufacturers. Each brand should be validated for each endemic region. Most rK39 RDTs are highly sensitive and specific in South Asia, but to date only the Bio-Rad IT-LEISHⓇ showed satisfactory sensitivity (85-90%) and specificity (90-99%) in immunocompetent patients in East Africa.

The kits are heat sensitive and can give misleading results if not stored correctly. All RDTs have a cut-off point that corresponds to a high antibody titre and so are unsuitable for detecting sub-clinical infections. They cannot be used to diagnose relapse, given that antibodies can be present in healthy patients for years after VL cure.

Notes

DISCLAIMER: LSHTM and partners collaborating in this video can take no legal responsibility for the use of any information contained. Users implementing the techniques shown do so at their own risk and must take responsibility for local verification/ validation of these techniques before they are used for the diagnosis of patients.