Abstract:

In order to understand the weakness of, and develop strategies for malaria microscopy in China, 12 participants of the 2017 World Health Organization-external competency assessment of malaria microscopists (WHO-ECAMM) were included in this study, consisting of 11 experts in provincial institutions, and 1 expert in a national-level institution. Their personal information and judgement results on blood slides were collected. Judgement on each slide was scored for each participant, and the associations of parasite density with the correctness of participants in species identification and parasite counting were analyzed. The associations of the score levels of participants with their work experience in microscopy and the average number of malaria cases in recent 3 years in the relevant province where they worked were analyzed. A total of 42 slides were used for species identification. Results showed that the participants had highest correctness rate in identifying slides with Plasmodium ovale and P. malariae [both (93.8 ± 4.0)%], followed by negative slides [(92.5 ± 2.2)%], P. faciparum [(78.3 ± 22.3)%] and P. vivax [(70.8 ± 14.2)%]. There was no correlation between parasite density and correct rate of participants in identifying P. faciparum slides (r = -0.13). Results of parasite counting showed that the average correctness rate of the participants was (42.2 ± 5.9)%. When the parasite density was less than 2 000/μl, the correctness rate of parasite counting was positively correlated with the density(r = 0.79). There were 2, 4, 3 and 3 participants scored levels 1, 2, 3, and 4, respectively. The level was not correlated with work experience (r = -0.16), but was negatively correlated with the average number of malaria cases in the province where they worked (r = -0.55). These results suggested that it is necessary to strengthen the training and practice in slide reading and species identification among microscopists, to maintain or improve their ability to diagnose malaria with microscopy.

Key words: Malaria, Microscopy, External competency assessment of malaria microscopists, Species identification, Parasite counting