Antigen capture immuno-chromatographic strip format in detecting parasite-specific lactate dehydrogenase to diagnose malaria in non-immune patients

ABSTRACT

Several rapid diagnostic test devices [RDT] based on detection of malaria antigen in the whole blood were developed. OptiMal test the presence of parasite-specific lactate dehydrogenase [LDH] enzyme using three monoclonal antibodies was used. Two monoclonal antibodies were pan-specific and recognized all malaria species. The third one was specific only for Plasmodium falciparum. The parasite antigens were detected using an antigen-capture immunochromatographic strip format. One hundred-nine malaria positive and 730 malaria negative cases diagnosed by microscopy were included. 75/109 were P. flaciparum 26 as P. vivax, 3 P. malariae and 5 mixed infection of P. falciparum and P. vivax. The RDT showed a low sensitivity [85%, 95% Confidence Interval [CI], 79-92%] with a much lower sensitivity in detecting species other than P. falciparum as well as in mixed infections. The sensitivity was 50% for less than 200 parasites/micro. The sensitivity of OptiMal for P. falciparum was 87% [95% CI,79-94], 81% [95% CI,66-96] for P. vivax, and failed with P. malariae. Mixed infections were misdiagnosed as P. falciparum. The sensitivity of OptiMal was quite good in detecting both P. falciparum and P. vivax [98%; 95%C1, 97-99 and 100%; 95%CI, 100-100 respectively] and 99% [95%CT, 98-99] for all species. The positive and negative ratio for all malaria species was [+LR= 62.3, -LR= 0.01]; for P. falciparum [+LR =3 8.9, -LR=0.01] and for P. vivax [+LR=0.8077/0,-LR=0.2]. The test value to assess drug resistance in post treatment days was discussed