Previously; it has been shown that only 8.6% of febrile pregnant women presented at Medani Hospital after initial general microscopist had P. falciparum malaria by referral lab examinations . In the current study light microscopy showed that 82 (64.1%) out of 128 pregnant women were positive for P. falciparum malaria. This might be explained by the extensive training to the general microscopists in the area following the previous results and the recommendations.
The main finding of the current study was a high performance in term of sensitivity (97.6%) and specificity 89.1% of Cyscope® fluorescence microscope in comparison with Giemsa-stained light microscopy as the gold standard. A sensitivity of 98.2% and specificity of 98.3% (gold standard: light microscopy) was obtained in cross-sectional facility-based analytical study of the diagnostic performance of the Cyscope® fluorescence microscope in Sudan . Recently, Nkrumah et al., reported a high sensitivity (100%) and specificity (97.4%) of the Cyscope® fluorescence microscope among Ghanaian children . However, in neighbouring Uganda in a large sample sized study involving women of child-bearing age and children from rural and peri-urban regions, high sensitivity (92.1% in adults and 86.7% in children) and low specificity (38.8% in adults and 28.6% in children) were observed for Cyscope® fluorescence microscope for malaria examination using Giemsa-stain light microscopy as the gold standard . Thus, application of Cyscope® fluorescence microscope in cross-sectional community-based studies leads to many false positives and this was attributed to small fluorescent bodies of unknown origin mistaken as malaria parasites . However, the false positives in the current study could be explained by the submicroscopic parasitaemia among these pregnant women. It has been shown that over one third of pregnant women in eastern Sudan had submicroscopic P. falciparum infections . In the current study there were two false positive cases. Because it was a small sample sized study, stratification of these results by parasite count might not be of value. Previously, the majority of false negatives diagnosed by fluorescent microscopy were of low parasitaemia according to light microscopy (≤400 parasites per μL of blood). The use of Plasmodium nucleic acid fluorescent dyes was found to facilitate detection of the parasites even in low parasitaemia conditions due to the contrast with the background . Recently, the sensitivity and specificity of the Cyscope® fluorescence microscope was 62.2% (95% CI, 56.3 to 67.8) and 96.0% (95% CI, 92.3 to 98.3), respectively using real-time PCR as the gold standard .
Generally, the accepted level of sensitivity for a rapid diagnostic test (RDT) in diagnosing malaria is a sensitivity of 95% at a parasite density of 100 parasites/μl . One of the limitations of the current study was that parasite counts were not performed by Cyscope® fluorescence microscope. Recently, it has been shown that parasite count obtained from Cyscope® fluorescence microscope were significantly lower than those obtained from Giemsa-stained light microscopy .
Thus, the affordable pricing, portability and compact design of the Cyscope® fluorescence microscope, and the fact that reagents do not require cold storage, make the method a potentially attractive alternative for malaria diagnosis in the rural setting . Furthermore, previous studies confirmed that Cyscope® fluorescence microscope requires very little training and has a short turnaround time of averagely 5 minutes per test [15, 16]. Yet, the disability of specific identification and differentiation of Plasmodia species as the disadvantage of Cyscope® fluorescence has to be remembered. Thus, Cyscope® fluorescence microscope would be very helpful in areas mainly endemic with P. falciparum. Generally RDTs are easy to perform by travelers and even for home management of malaria. Moreover RDTs distinguishes Plasmodium species although they are less accurate in this respect than microscopy.