Abstract:

To understand and evaluate the quality of malaria blood smears in all provinces of China, provide data support for guiding the quality control of malaria microscopic examination during post-malaria elimination, and explore the standard model of evaluating the capability of preparing malaria blood smears. One blood smear of the first malaria case in a month in each province(direct-administered municipalities and autonomous regions) was collected, with a total of 5 cases or more in 2019. Provinces without malaria cases were provided with negative blood smears during malaria screening. Ten experts with WHO external assessment level 1 or level 2 certificates of malaria microscopy capability were organized to form two quality assessment teams. Fifteen assessment criteria (①-) were determined. All blood smears were divided into two groups for each province and sent to two teams of experts for double-blind reading evaluation. The single blood smear score and the qualified rate of blood smear in different provinces (15 points for each blood smear, 13 points for qualified) were calculated. The level of blood smear preparation in each province was graded (the qualification rate ≥ 90%, 80%-90%, 70%-80%, < 70% were A, B, C and D, respectively). The institutes that prepared the blood smears at different provinces were divided into provincial laboratories and non-provincial laboratories, and the differences of average single blood smear scores and preparation grades among different laboratories were compared. The average score rates of all blood smears were calculated and compared according to each evaluation standard. The average scores of blood smears between different laboratories were compared by t-test, and the levels of blood smears were compared by Person chi-square test or Fisher exact probability method. A total of 285 blood smears were collected from 28 provinces. The national average single blood smear score is (13.3 ± 1.5) with the highest score being 14.8 points, the lowest being 8.9 points, and the median being 13.6 points. The total rate of satisfied blood smears was 72.6% (207/285). The highest satisfaction rate in all provinces was 100%, and the lowest was 20%. The number of provinces categorized into A, B, C and D levels were 11, 3, 2 and 12, respectively. The average score in provincial laboratories was (14.2 ± 0.2), higher than that in non-provincial laboratories [(13.0 ± 0.4)] (t = 2.3, P < 0.05). Among the 15 provinces in which blood smears were prepared by non-provincial laboratories, 4 were marked as level A, 2 were marked as level B and 9 were marked as level D. Among the 9 provinces in which blood smears were prepared by provincial laboratories 6 were marked as level A, 1 was marked as level B, 1 was marked as level C, and 1 marked as level D. The level of preparing blood smears in the provincial laboratories was higher than that in the non-provincial laboratories (Fisher exact probability method, P < 0.05). The coefficient of variation of the average single blood smear score among different provinces (municipalities, autonomous regions) was 11.2%, and the coefficient of variation of the qualification rate was 37.5%. Nationally, the scoring rate of blood smear in items ②, ③, ⑧, ⑨, and of the evaluation criteria is low (74.8%-85.3%), which was mainly due to the unsatisfied thick blood smears. The main deducted points in provincial laboratories marked as level C are and, which mainly show that there are many contaminants in the blood smears after staining, and the staining is poor. The deducted points in the provincial laboratory marked as level D were ⑩, and. The main reason is that no red blood cells are observed in the thin films, and the protozoal morphology has changed. The levels of preparing blood smears varied in different provinces. The levels of preparing blood smears in provincial laboratories were higher than those in non-provincial laboratories. Normalized operation in preparing blood smears in basic units should be strengthened.

Key words: Malaria, Rate of qualified blood smear, Blood smear, Quality control