The main findings of the current study were that the RDT kit had moderate sensitivity (83.3%) and acceptable specificity (92.0%) for the diagnosis of peripheral P. falciparum among febrile pregnant women, but low sensitivity (17.4%) and specificity (81.7%) for diagnosing placental malaria when compared with PCR as the gold standard. The performance of the same brand of kit (SD Bioline P.f / P.v) was recently compared with PCR in eastern Sudan among febrile non-pregnant patients where it was found to have a sensitivity of 69% and specificity of 84% . Recently low sensitivity (31.8%) but full specificity (100%) was reported for RDT kits used during pregnancy in Uganda, where PCR was used as the gold standard . The performance of the RDT kit for malaria diagnosis used in the current study is in agreement with the findings of Schachterle et al., who showed that RDT kits had high false positive and negative rates in a region of malaria hypoendemicity in Tanzania . However, the results of the later study were based on microscopy data without PCR correction. Furthermore, Mayor et al.,  have recently shown that among the 122 women that were PCR-positive for P. falciparum (as judged by peripheral and/or placental blood sampling) 87 (71.3%) and 74 (60.7%) were not considered positive by peripheral microscopy and the HRP2 RDT, respectively.
Nevertheless, it has been observed that RDT had high sensitivity (96.8%) and specificity (73.5%) for the diagnosis of P. falciparum malaria among febrile pregnant women in a hyper-endemic region in Uganda, when compared with microscopy as the gold standard . However, it was observed that the RDT had a modest level of accuracy (80.9% sensitivity, 87.5% specificity) for detecting placental malaria using peripheral blood at time of delivery, in the later study . Recently, the prevalence of placental infection, as determined by microscopy and RDT, was 5.1% and 5.0%, respectively, with highly significant agreement (82.9%); however discordances were observed between the two methods at low level parasitaemias . Previous studies conducted at the time of birth have shown that RDT detecting P. falciparum HRP2 are more sensitive than blood smears, and appear to be reliable predictors of adverse outcomes of malaria in pregnancy [30–32].
Although the manufacturer’s (Bio Standard Diagnostics, Gurgaon, Korea) instructions were strictly followed, the poor performance this RDT kit in the current study is disappointing, and perhaps somewhat difficult to explain. Furthermore, the RDT used in the current study was very sensitive and specific when evaluated by WHO/ FIND . High sensitivity is needed to provide confidence to the practicing physician that the RDT is unlikely to miss a malaria infection in pregnancy. However, the PPV was very low (14.3%); this could be due to false positive results, possibly attributable to the persistent nature of HRP-2 antigenaemia that has been documented already in previous studies [33, 34]. It should be mentioned that HRP2 based RDT positivity among pregnant women can persist for up to 28 days after antimalarial drug treatment, especially among women with low gravidity and those with a higher parasite density at enrolment . It seems to be still there is a great challenge in diagnosing malaria and its treatment adverse effects and associated anemia [35–37].
The Sudanese National Malaria Control Programme recommends the use of RDT in those settings where no expert microscopy is available, and maintains microscopic examination in those places where microscopy is of an adequate level. This RDT strategy was investigated earlier in Sudan for the home management of malaria using artemisinin-based combination therapy . Therefore, based on the findings of the current study, it appears likely that implementation of malaria RDT in Sudan in settings where microscopic expertise is available should not be recommended.