The species-specific forms of lactate dehyrogenase
The malarial parasite forms of lactate dehydrogenase (pLDH) are specific forms of the LDH enzyme that is part of the malaria glycolytic pathway. pLDH is distinct from human forms of LDH allowing all parasite species to be identified by this LDH forms. However there are also species-specific forms that can be individually useful.
P.falciparum-specific LDH (PfLDH). This form has very good sensitivity at high parasitaemia (exceeding 90%), althought at lower parasite levels (<1000 parasites/ μL) sensitivity of PfLDH may be less than that of HRP2 (around 45%). A potential advantage of PfLDH over HRP2 is that it is evolutionarily conserved antigen and does not have reported gene-delection mutants so may be an effective choice where malaria arises in ares with high rates of HRP2 deletion.
P.vivax-specific LDH (PvLDH). This form has value for the specific diagnosis of P.vivax and may be useful 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%).
Note LDH antgens are relatively rapidly cleared from the blood, so have potential value in testing response to treatment or for malaria testing in recently infected patients.
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