[Laboratory malaria re-examination and evaluation of malaria diagnostic capability in Shanghai Municipal Malaria Diagnostic Reference Laboratory from 2017 to 2022].

Abstract

Objective: To evaluate the malaria diagnostic capability in Shanghai Municipal Malaria Diagnostic Reference Laboratory from 2017 to 2022 and to analyze factors affecting the diagnosis results, so as to provide the scientific evidence for increasing the laboratory malaria diagnostic capability during the post-elimination stage.

Methods: Plasmodium-negative blood smears were randomly sampled using a proportional sampling method each quarter during the period from 2017 to 2022 and scored by Shanghai Municipal Malaria Diagnostic Reference Laboratory. Malaria cases' blood samples from district centers for disease control and prevention in Shanghai Municipality were re-reviewed using microscopy and multiplex PCR assay to evaluate the capability of malaria diagnosis.

Results: A total of 7 746 quality control blood smears were collected from district centers for disease control and prevention in Shanghai Municipality from 2017 to 2022, with a mean score of (76.74 ± 14.34) points and a qualification rate of 86.65% (6 712/7 746). A total of 387 blood smears were re-reviewed from 2017 to 2022, with an overall coincidence of 96.38% (373/387) for malaria diagnosis and 95.06% (308/324) for parasite species identification, and there were no significant differences in the coincidence for either malaria diagnosis (χ² = 2.57, P > 0.05) or parasite species identification among years (χ² = 1.04, P > 0.05). A total of 384 whole blood samples were collected from district centers for disease control and prevention, and the detection of whole blood samples was 70.31% (270/384) in district centers for disease control and prevention. All 384 whole blood samples were re-reviewed by Shanghai Municipal Malaria Diagnostic Reference Laboratory using a multiplex PCR assay from 2017 to 2022, with an overall coincidence of 94.07% (254/270) for malaria diagnosis and 99.55% (223/224) for parasite species identification, and there were no significant differences in the coincidence for either malaria diagnosis (χ² = 5.77, P > 0.05) or parasite species identification among years (χ² = 8.37, P > 0.05). The overall coincidence rates of Plasmodium-positive and negative whole blood samples were 100.00% (224/224) and 65.22% (30/46) in district centers for disease control and prevention, with a significant difference (χ² = 82.82, P < 0.001), and there was a significant difference in the coincidence rate for identification of P. falciparum, P. vivax, P. malariae and P. ovale (χ² = 24.28, P < 0.001). A total of 1 584 blind blood smears subjected to microscopic examinations by centers for disease control and prevention and medical institutions across all districts in Shanghai Municipality from 2017 to 2022, with a 96.15% (1 523/1 584) correct rate for malaria diagnosis and 85.07% (1 003/1 179) for parasite species identification, and there were significant differences in the correct rate of both malaria diagnosis (χ² = 20.98, P < 0.001) and parasite species identification among years (χ² = 70.77, P < 0.001). A total of 320 blind nucleic acid samples from malaria cases were tested, with a 99.38% (318/320) correct rate for malaria diagnosis and 100.00% (225/225) for parasite species identification, and there was no significant difference in the correct rate of malaria diagnosis among years (χ² = 6.04, P > 0.05).

Conclusions: There were still shortcomings in blood smears preparation, microscopic examinations and nucleic acid testing in centers for disease control and prevention across all districts in Shanghai Municipality from 2017 to 2022. A greater role in the quality control of malaria diagnosis is recommended for Shanghai Municipal Malaria Diagnostic Reference Laboratory to prevent the re-establishment of imported malaria and consolidate the elimination achievements.