Plasmodium lactate dehydrogenase (PLDH)

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Use of PfLDH and PvLDH in diagnosis The pLDH assays identify enzymes of the malaria glycolytic pathway, the proteins are distinct from human forms of LDH allowing them to be identified by RDT tests. The LDH antgens are relatively rapidly cleared from the blood, so have value in testing response to treatment or for malaria testing in recently infected patients.There are species-specific forms of LDH, these underle the P.falciparum and P.vivax forms of LDH. There are three forms of species-specific LDH antigen: PfLDH - specifically detects a form expressed by P.falciparum detecting the species with good sensitivity PvLDH - detecting the parasite form of LDH that is specific for P.vivax Note that the non-species-specific form (PpanLDH) is also widely used (see separate description) Characteristics of species-specific forms of LDH 1. P.falciparum-specific (PfLDH): has very good sensitivity at high parasitaemia that may meet or exceed 90%. However, at lower parasite levels (<1000 parasites/ μL) sensitivity of PfLDH may be less than that of HRP2 (around 45%). An additioanl potential advantage over HRP2 sould be considered - this conserved antigen does not have reported gene-delection so may be an effective choice where malaria arises in ares with high rates of HRP2 deletion. 2. P.vivax-specific (PvLDH): has value for the specific diagnosis of P.vivax in areas where this is a dominant species (e.g. areas of South America). PvLDH RDTs probably have similar sensitivity for P.vivax as the PpanLDH (of around 70-90% at high paraitaemia, declining when parasite levels are low - around 30-60%), however they do not cross-react with P.vivax giving them value in distinguishing these two species.