Diagnosis of malaria and typhoid fevers using basic tools: a comparative analysis of a retrospective data with a prospective evaluation in an endemic setting
Malaria and typhoid fever are among important and endemic diseases in the tropical countries such as Nigeria. Diagnosis of most cases of malaria/typhoid co-infections are based on clinical suspicion alone or unreliable diagnostic tools leading to poor or misdiagnosis. A retrospective analysis was conducted on the positivity rate for malaria parasite and typhoid fever among patients who attended the Bayero University, Kano (BUK) Health Clinic from January to December 2013. A prospective study was also carried out on 200 febrile patients and 80 apparently healthy subjects (controls) with the view to determine the diagnostic profiles of malaria and /or typhoid fever co-infection using standard protocols (microscopy, rapid diagnostic test (RDT) for malaria parasite (MP), Widal test, stool and blood cultures for typhoid fever). Both test and control subjects were evaluated for the presence or otherwise of the malaria and /or typhoid aetiologic agents. Results obtained from the retrospective study for the period January to December 2013 indicated that, of the 2362 tests conducted, 318 (13.5%) were positive for MP using RDT and 722 (30.6%) were positive for typhoid fever using Widal test. Co-infection rate obtained was 89 (3.8%). Of the 200 subjects evaluated for the prospective study however, 42 (21%) and 34 (17%) were positive for MP using microscopic technique and RDT respectively. Microscopy was established to be more sensitive than RDT. Eighty nine (45%) were Widal positive. The culture method for typhoid fever diagnosis was negative. Co-infection rate stood at 17 (8.5%). No association however was found between the two disease conditions (p=0.6032). Significant proportion of the patients 86 (43%) were neither positive for malaria nor for typhoid fevers. Three isolates of non-typhoid salmonella specie and three other bacterial isolates were recovered from the stool and blood samples of the patients respectively. Baseline titre value for Widal test at BUK community was established as 160 and above for O antibodies to S. typhi, hence the criterion employed in the prospective evaluation. Laboratory evidence of malaria and typhoid co-infection rate at a titre of ≥160 was 8.5% using microscopy and 7% using RDT. The use of RDT is simple and easy, but has less sensitivity, thus may leave some patients with malaria un-detected. Based on the results of these findings, vis a vis the proportion of individuals negative for both malaria and typhoid fevers, clinicians should revisit causes of febrile illnesses other than malaria or typhoid and hence the need to include other tests for the detection of other causes.
Keywords: Malaria diagnosis, Typhoid fever, RDT, Widal test, Co-infections, Nigeria