Comparison of Two Commercial Assays with Expert Microscopy for Confirmation of Symptomatically Diagnosed Malaria

Abstract

Conventional light microscopy has been the established method for malaria diagnosis. However, recently several nonmicroscopic rapid diagnostic tests have been developed for situations in which reliable microscopy may not be available. This study was conducted to evaluate the diagnostic performance of a recently introduced ICT Malaria Pf/Pv test. This assay detects Plasmodium falciparum histidine-rich protein 2 antigen (PfHRP-2) for P. falciparum diagnosis and pan-malarial antigen for P. vivax diagnosis. In this study we compared the performance of ICT Malaria Pf/Pv with microscopy of Giemsa-stained blood films and with an OptiMAL test that detects Plasmodium lactate dehydrogenase (pLDH) antigen. A total of 750 clinically suspected malaria patients were examined at local health centers in Kuwait. Both the antigen tests had a high degree of specificity (>98%) for detection of malaria infection. However, they were less sensitive than microscopy. Compared with microscopy the ICT Malaria PF/pf test failed to detect malaria infection in 93 (34%) of 271 malaria patients (11% of patients with P. falciparum and 37% of patients with P. vivax) and the OptiMAL test failed to detect malaria infection in 41 (15%) of 271 malaria patients (7% of patients with P. falciparum and 13% of patients with P. vivax). The sensitivities of the ICT Malaria Pf/Pv and OptiMAL tests for detection of P. falciparum infection were 81 and 87%, and those for detecting P. vivax were 58 to 79%, respectively. The sensitivity of the ICT Malaria Pf/Pv and OptiMAL tests decreased significantly to 23 and 44%, respectively, at parasite densities of <500/l. Both of the tests also produced a number of false-positive results. Overall, the performance of the OptiMAL test was better than that of the ICT Malaria Pf/Pv test. However, our results raise particular concern over the sensitivity of the ICT Malaria Pf/Pv test for detection of P. vivax infection. Further developments appear necessary to improve the performance of the ICT Malaria Pf/Pv test.

Efficacy of Immunodiagnosis of Falciparum Malaria at Different Levels of Parasitemia

“…In a study in Kuwait, Iqbal et al found 96% sensitivity when parasitemia was >500 parasites/µL and 44% sensitivity when parasitemia was <500 parasites/µL. 7 Kakkilaya in 2003 observed that many studies showed >95% sensitivity when parasitemia was 500 parasites/µL. 13 From the above discussion it is observed that some results are consistent with our findings and some remarkably differ from the present study.…”

“…Among all the methods, microscopic examination of blood film is regarded as the 'gold standard'. 6,7 This method is relatively simple and cost-effective. But it is time consuming, needs expert microscopist and sensitivity is questionable at low level of parasitemia.…”

Malaria: A disease that should not be forgotten in emergency service; Case Report

“…Özellikle ataklar sırasında bakıldığında gerek kalın, gerekse ince yayma preparatlarında etkeni görme şansı oldukça yüksektir. [11] Bizim olgumuzda sıtmayı düşündüren hastanın ateşinin seyri ve seyahat öyküsüydü. Periferik yayma ve kalın damla incelemesi ile sıtma tanısını konuldu.…”

<strong>A portable image-based cytometer for rapid malaria detection and quantification</strong>

“…However, these methods rely on detection of antigens derived from the parasites, rather than detecting the parasites themselves. Though RDTs are often able to differentiate most malarial species by means of their antigenic properties, overall sensitivity of detection is far below the threshold of microscopy-based malaria detection, exhibiting huge variations among the patients [11][12][13][14][15] and failing to guide treatments which could be fatal when mixed infections occur [16]. These are efficient methods; however the results can vary depending on the severity of infection and the high occurrence of young parasitic forms (ringstage infections) in the peripheral blood, which are only beginning to establish metabolic processes.…”