Quality assessment of malaria microscopic diagnosis at the Aristide Le Dantec University Hospital of Dakar, Senegal, in 2020

BACKGROUND

Following WHO guidelines, microscopy is the gold standard for malaria diagnosis in endemic countries. The Parasitology-Mycology laboratory (LPM) is the National Reference Laboratory and is currently undergoing ISO 15189 accreditation. In this context, we assessed the performance of the laboratory by confirming the reliability and the accuracy of results obtained in accordance with the requirements of the ISO 15189 standards. This study aimed to verify the method of microscopic diagnosis of malaria at the LPM, in the Aristide Le Dantec hospital (HALD) in Dakar, Senegal.

METHODS

This is a validation/verification study conducted from June to August 2020. Twenty (20) microscopic slides of thick/thin blood smear with known parasite densities (PD) selected from the Cheick Anta Diop University malaria slide bank in Dakar were used for this assessment. Six (6) were used to assess microscopists' ability to determine PD and fourteen (14) slides were used for detection (positive vs negative) and identification of parasites. Four (4) LPM-HALD microscopists read and recorded their results on prepared sheets. Data analysis was done with Microsoft Excel 2010 software.

RESULTS

A minimum threshold of 50% concordance was used for comparison. Of the twenty (20) slides read, 100% concordance was obtained on eight (8) detection (positive vs negative) slides. Four (4) out of the six (6) parasite density evaluation slides obtained a concordance of less than 50%. Thirteen (13) out of the fourteen (14) identification slides obtained a concordance greater than 50%. Only one (1) identification slide obtained zero agreement from the microscopists. For species identification a concordance greater than 80% was noted and the microscopists obtained scores between 0.20 and 0.4 on a scale of 0 to 1 for parasite density reading. The microscopists obtained 100% precision, sensitivity, specificity and both negative and positive predictive values.

CONCLUSION

This work demonstrated that the microscopic method of malaria diagnosis used in the LPM/HALD is in accordance with the requirements of WHO and ISO 15189. Further training of microscopists may be needed to maintain competency.

Ultrastructure of spermiogenesis and the spermatozoon of Nomimoscolex sp. (Cestoda, Proteocephalidea) intestinal parasite of Clarotes laticeps (Fish, Teleost) in Senegal

Spermiogenesis in Nomimoscolex sp. begins with the formation of a differentiation zone delimited at the front by arched membranes. It is bordered by cortical microtubules and contains two centrioles surmounted each by striated roots. The latter are linked together at their bases by a thin layer of electron-dense material. The two centrioles give each a flagellum that rotates and fuses with the median cytoplasmic extension. The nucleus elongates, becomes filiform and migrates between the axonemes in the cytoplasmic extension. During the nuclear migration, crested-like bodies form. After the migration of the nucleus, the old spermatid separates from the residual cytoplasm by strangulation of the ring of arched membranes. The mature spermatozoon of Nomimoscolex sp. lacks mitochondria, is filiform and tapered at both its extremities. Its anterior end exhibits an apical cone of electron-dense material and three crested-like bodies of unequal length coiled in a spiral on its periphery. The axoneme is of the 9 + 1' pattern. The cortical microtubules are parallel to the spermatozoon axis. The nucleus is a fibrous cord of partly condensed chromatin. The cytoplasm is slightly dense but contains many electron-dense granules in regions II and III of the spermatozoon. Crested-like bodies and striated roots linked together by an electron-dense material have never been reported during the spermiogenesis in a proteocephalidean. In addition we describe for the first time the existence of three crested-like bodies in the Proteocephalidea.