The dilemma of malaria diagnosis: How accurate are the diagnostic tools?

Abstract

Background: Malaria represents a major health problem for the public as well as clinicians and diagnosticians, because many diseases have similar symptoms to the symptoms of malaria. This study aimed to determine the accuracy of malaria diagnosis both clinically and using various laboratory tests compared to the gold standard microscopy.

Materials and Methods: This is a descriptive, cross-sectional hospital-based study, conducted at the casualty of Atbara Hospital, in January 2011. Any patient clinically suspected to have malaria in this month was included. Demographic and clinical data was collected using a standardized pre-tested questionnaire. Each patient was diagnosed primarily by the clinician, mainly medical officers and houseofficers, investigated by a thick blood film stained by Giemsa stain in the hospital laboratory. We, thereafter, obtained blood samples from the same patient, made thick and thin films stained by Giemsa and Field stains in addition to rapid tests for malaria antigens and antibodies. For quality assurance, tests were reviewed by expert technicians in the State Reference Laboratory for Malaria. Giemsa thick blood film was taken as the gold standard. Results of the various diagnostic methods were compared.

Results: Two hundred patients volunteered to participate in this study. Females were 121(60.5%). The age range was from 7 months to 70 years, mean 25.85(+20.5). Only 5(2.5%) cases were confirmed positive for malaria. When compared to the gold standard test, giemsa thin film and Field stain showed 100% sensitivity and 100% specificity. The sensitivity and specificity of the blood film done by hospital laboratory was 80% and 99.5% respectively. While Rapid Antibody scored 60% and 89.7%, and for Rapid Antigen scored 80% and 96.9% for the sensitivity and specificity respectively. The clinical diagnosis was the least accurate method 80% sensitivity and 38.5% specificity.

Conclusion: The prevalence of malaria among symptomatic patients in Atbara hospital is low. The ICT antigen and antibody tests, as well as clinicians over diagnose malaria when compared to the blood film. A combination of Rapid Diagnostic Test (RDT) with thick blood film for suspected malaria cases is recommended.

Keywords: Malaria, Diagnosis, Blood film, Sudan