A Comparison of TPI Gene-Specific PCR and Stool Microscopy in Detecting Giardia lamblia Infection in Western, Kenya

Abstract

Background and study aim: Giardia lamblia is a widespread pathogen of gastrointestinal infection in Kenya, the diagnosis of which is mostly based on stool microscopy. Molecular assays against conserved genes e.g. Triose Phosphate Isomerase (TPI) provide better detection. The objective of the study was to determine the diagnostic accuracy of TPI gene-specific PCR in the identification of G. lamblia in symptomatic patients in western Kenya with the colon microscopy used as the comparator. Patients and Methods: This was a cross-sectional study that was carried out among 147 patients who had presented with gastrointestinal symptoms at Busia County referral Hospital, western Kenya. Direct microscopy of stool samples and TPI gene-specific PCR were used to analyze the samples. Results: G. lamblia was identified in 78 (53.1) of the participants by microscopy and 53 (36.1) of the participants by TPI-PCR. TPI-PCR had sensitivity of 66.7% (95% CI: 55.1-76.9) and specificity 98.6% (95% CI: 92.3 -100). The predictive value (positive and negative) is 98.1 and 72.3 with the overall diagnostic accuracy standing at 81.6. Methods had a great deal of agreement (Cohen kappa = 0.639). The McNemar’s test showed that there was significant discordance (P < 0.0001). The participants who were positive by microscopy were 136 times more likely to be positive by TPI-PCR as compared to the negative (OR = 136; 95% CI: 17.9-1035.2, P = 0.00001). Conclusion: TPI gene-specific PCR was highly specific, generally diagnostic in its overall performance and showed a high agreement with stool microscopy but sensitivity was moderate.