Combination Rapid Diagnostic Tests Evaluated for Malaria in Pregnancy

The potential risk of Plasmodium falciparum or P. vivax malaria and the corresponding risk of malaria associated maternal anemia and low birth weight due to pre-term delivery or intra-uterine growth retardation needs to be urgently addressed.

An international team of scientists led by those at the Liverpool School of Tropical Medicine (UK) enrolled pregnant women of any gravidity aged between 15 and 49 years who attended clinics for routine antenatal care between March and July 2012. A finger prick blood sample was taken to simultaneously test the four rapid diagnostic tests (RDTs), malaria microscopy and dried blood spots for polymerase chain reaction (PCR).

Thick and thin smears were made on the same slide and stained with 5 % Giemsa. A slide was declared negative if parasites were absent after examining 200 high power fields. Parasite density was quantified against 300 leukocytes on an assumed leukocyte count of 8,000/µL of blood. The four HRP-2/pLDH RDTs included Parascreen Rapid Test Pan/Pf (Zephyr Biomedical System; Goa, India); SD Bioline Malaria Ag Pf/Pan (Standard Diagnostic Inc.; Suwon City, Republic of Korea); CareStart Malaria pLDH/HRP2 combo (Access Bio Inc.; Somerset, NJ, USA); the two RDTs used in the malaria control program in Indonesia at the time of the study, and First Response Malaria pLDH/HRP-2 combo (Premier Medical Corporation Ltd.; Kachigam, India). Nested PCR was performed on all samples to detect malaria parasites and for speciation.

Overall 950 women were recruited and 98.7% were asymptomatic. The prevalence of malaria was 3.0% to 3.4% by RDTs, and 3.6% by field microscopy, 5.0% by expert microscopy and 6.6% by PCR, The geometric-mean parasite density was low, P. falciparum = 418 parasites/µL, and P. vivax = 147/µL. Compared with PCR, the overall sensitivity of the RDTs and field microscopy to detect any species was 24.6% to 31.1%; specificities were greater than 98.4 %. Relative to PCR, the First-Response RDT had the best diagnostic accuracy for any species with the sensitivity = 31.1 %, and specificity = 98.9 %.

The authors concluded that the diagnostic accuracy to detect malaria among mostly asymptomatic pregnant women and perceived ease of use was slightly better with First-Response, but overall, differences between the four RDTs were small and performance comparable to field microscopy. Combination RDTs are a suitable alternative to field microscopy to screen for malaria in pregnancy in rural Indonesia. The clinical relevance of low density malaria infections detected by PCR, but undetected by RDTs or microscopy needs to be determined. The study was published on October 29, 2015, in the Malaria Journal.

Related Links:
Liverpool School of Tropical Medicine 
Zephyr Biomedical System 
Access Bio Inc.