The accuracy of diagnostic testing is key in informing malaria case management, however, data on the performance of malaria diagnostics in private health facilities in Uganda is still limited. We evaluated the accuracy of malaria microscopy and factors associated with inaccurate microscopy in 16 private facilities in Entebbe municipality, Uganda. Our findings show that although the accuracy and negative predictive values of the facility-based microscopy in the participating facilities was very high, the positive predictive value was relatively poor (63.0%), with over 1/3rd of the patients diagnosed with malaria not actually having malaria. The factors associated with a participant having inaccurate malaria smear results included having the smear read by a technician having less than five years’ experience in reading malaria smears and having smears read by a technician whose facility was examining less than 5 smears a day.
Accurate diagnosis of malaria is vital for effective management and control of malaria. In Uganda, microscopy remains the gold standard for malaria diagnosis [3]. Malaria microscopy has advantages over rapid diagnostic tests (RDTs) in that it can be used to differentiate malaria species and quantify the parasitaemia and therefore is more informative in terms of the most appropriate care to provide a patient [20]. In this study, microscopy was highly accurate, however, one third of the patients diagnosed as having malaria did not actually have the disease. These results provide some assurance that microscopy is still a reliable tool for detecting patients with malaria that present to the private health sector in Uganda. However, the results also raise concerns that a number of patients diagnosed with malaria in this setting, where most patients are first treated in the country [21] may not actually have the disease, resulting in over-diagnosis of malaria. Overdiagnosis of malaria is of concern as it results in antimalarial drug misuse which may increase the risk of drug resistance, costs to the patient, and missing the true diagnosis for the presenting symptoms.
Although present, the observed rates of malaria over-diagnosis study are still much lower than what has been previously recorded in the country. Outpatient malaria over-diagnosis rates are massive in Uganda, reaching as high as 79% in public health facilities [6, 22]. Some improvement in malaria microscopy has been realized in the last decade, and this has been attributed to in-service training and continuous support supervision [16, 23]. However, in this study, to the best of our knowledge, no in-service training activities have been conducted in the private facilities in the study area in the last 10 years. We therefore do not attribute the differences in performance observed in this study to in service training, but may be due to the facilities taking care of fewer manageable numbers of patients compared to the overwhelming patient loads in public facilities, allowing them time to correctly stain and examine the slides.
It is also important to note that only two of the laboratory technicians were responsible for majority of the inaccurate results. Poor microscopy has been associated with multiple factors including; 1) poor training, supervision, and skills maintenance, 2) poor slide preparation techniques, 3) very heavy workloads, 4) poor condition of the microscope, and 5) lack of quality essential laboratory supplies [24–26]. In this study, the experience of the laboratory technologist conducting the smear reading was significantly associated with having inaccurate results. Experience in this study was through either reading many blood smears a day or having more years of reading malaria smears. Experience has previously been highlighted as an important factor in improving the accuracy of malaria microscopy[27] and the WHO recommends reading of at least 10 slides a month in order to maintain the competence of correctly trained microscopists [28].
The team recognizes some limitations in the study including; 1) The study team was stationed at the participating facilities and conducted exit interview with patients seen in the laboratory. This could have modified the behavior of the laboratory technologists such that more attention was paid to the smear reading than routinely practiced. Indeed studies have reported that medical personnel often modify behavior when they are aware that they are being observed [29]. We attempted to minimize this by not revealing to the facility personnel that the disease of interest was malaria but were interested in patients sent to the laboratory. In addition, the study staff spent up to two months at the facilities and we believe that any change in routine practices that may have occurred at the start of the study may have been reverted by the time the study came to an end which is what is often observed in similar studies [29]. 2) Entebbe municipality is an urban area with unique characteristics that may not be similar to other regions in Uganda and thus limiting the generalizability of results to settings similar to the study area.
In conclusion, the accuracy of malaria microscopy in the private facilities in Entebbe Municipality was high, although one third of patients diagnosed with malaria did not have the disease. Majority of the errors in smear readings were made by two laboratory technicians, and the main factor associated with inaccurate smear results was low experience in malaria microscopy. In-service training may be sufficient to eliminate inaccurate smear results in this setting, and these private facilities would be ideal model facilities to improve the quality of malaria microscopy in Uganda especially in the public sector.