Comparison of the OptiMAL Test with PCR for Diagnosis of Malaria in Immigrants

Abstract

The OptiMAL test (Flow Inc., Portland, Oreg.), which detects a malaria parasite lactate dehydrogenase (pLDH) antigen, has not been evaluated for its sensitivity in the diagnosis of malaria infection in various epidemiological settings. Using microscopy and a PCR as reference standards, we performed a comparison of these assays with the OptiMAL test for the detection of Plasmodium falciparum andPlasmodium vivax infection in 550 immigrants who had come from areas where malaria is endemic to reside in Kuwait, where malaria is not endemic. As determined by microscopy, 125 (23%) patients had malaria, and of these, 84 (67%) were infected with P. vivax and 36 were infected with P. falciparum; in 5 cases the parasite species could not be determined due to a paucity of the parasites. The PCR detected malaria infection in 145 (26%) patients; 102 (70%) of the patients had P. vivax infection and 43 had P. falciparum infection. Of the five cases undetermined by microscopy, the PCR detected P. falciparuminfection in two cases, P. vivax infection in two cases, and mixed (P. falciparum plus P. vivax) infection in one case. Correspondingly, the OptiMAL test detected malaria infection in 95 patients (17%); of these, 70 (74%) hadP. vivax infection and 25 were infected with P. falciparum. In this study, 61 (49%) of the 125 malaria cases, as confirmed by microscopy, had a degree of parasitemia of <100 parasites per μl, and 23 (18%) of the cases had a degree of <50 parasites per μl. Our results show that the sensitivity of the OptiMAL test is high (97%) at a high level of parasitemia (>100 parasites/μl) but drops to 59% when the level is <100 parasites/μl and to 39% when it is <50 parasites/μl. In addition, the OptiMAL test failed to identify four patients whose blood smears contained P. falciparumgametocytes only. We conclude that the sensitivity and specificity of the OptiMAL test are comparable to those of microscopy in detecting malaria infection at a parasitemia level of >100 parasites/μl; however, the test failed to identify more than half of the patients with a parasitemia level of <50 parasites/μl. Thus, the OptiMAL test should be used with great caution, and it should not replace conventional microscopy in the diagnosis of malaria infection.

Sensitive detection and accurate monitoring of Plasmodium vivax parasites on routine complete blood count using automatic blood cell analyzer (DxH800TM)

“…, 2008). None of the other tests for diagnosis of malaria demonstrated such sensitivity and specificity (Iqbal et al. , 1999; Iqbal, Sher & Rab, 2000; Moody, 2002; Hänscheid et al.…”

“…The proper diagnosis of P. vivax malaria is based on clinical signs and symptoms, and can be accomplished by microscopic examinations of blood, rapid diagnostic tests, immunofluorescence assay, polymerase chain reaction (PCR), microarray, flow cytometry, and automatic blood cell analysis (Iqbal et al. , 1999; Iqbal, Sher & Rab, 2000; Moody, 2002).…”

Comparison of three antigen detection methods for diagnosis and therapeutic monitoring of malaria: a field study from southern Vietnam

“…The performance of all of the tests fell away at relatively low parasitaemias, consistent with the findings of others (Fryauff et al . 2000; Iqbal et al . 1999; Lema et al .…”

“…2000). Nevertheless, some of this variability may also be explained by the relatively poor performance of OptiMAL ® at low parasitaemias (< 500/μl) (Iqbal et al . 1999; Fryauff et al .…”

Evaluation of the Abbott Cell‐Dyn 4000 hematology analyzer for detection and therapeutic monitoring of Plasmodium vivax in the Republic of Korea

“…When the level of parasitaemia is low, diagnosis by Giemsa‐stained blood smears requires long periods of observation by experienced microscopists (Moody 2002). This problem persists even with the advent of several alternative methods such as rapid dipstick tests (Iqbal et al. 1999, 2000; Cho et al.…”