Journal of Clinical Microbiology, November 1999, p. 3644-3646, Vol. 37, No. 11
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Microbiology,
Received 19 March 1999/Returned for modification 26 April
1999/Accepted 7 July 1999
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 and
Plasmodium 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. falciparum
infection 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%) had
P. 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. falciparum gametocytes 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.
*
Corresponding author. Mailing address: Department of
Microbiology, Faculty of Medicine, Kuwait University, P.O. Box 24923, Safat 13110, Kuwait. Phone: (965) 531 2300, ext. 6781. Fax: (965) 533 2719. E-mail: iqbal{at}hsc.kuniv.edu.kw.
This article has been cited by other articles:
| Antimicrob. Agents Chemother. | Clin. Microbiol. Rev. |
|---|---|
| Clin. Vaccine Immunol. | ALL ASM JOURNALS |
|---|