Nsambi. R. (2025), Comparative Evaluation of Real-Time PCR and Kato-Katz Microscopy for the Detection and Quantification of Giardia intestinalis in Lakeshore Communities of Buikwe and Buvuma Districts. (Unpublished Master's Dissertation) Makerere University, Kampala, Uganda.

Abstract

Background: Giardia intestinalis is a significant cause of waterborne diarrheal disease globally, particularly in communities with poor sanitation and limited access to clean water. Accurate diagnosis is crucial for effective control, yet the widely used Kato-Katz microscopy method has limited sensitivity, especially for low-intensity and asymptomatic infections. This study aimed to develop and validate a Real-Time Polymerase Chain Reaction (Real-Time PCR) assay for the sensitive detection and quantification of G. intestinalis and to compare its performance with the conventional Kato-Katz technique in lakeshore communities of Buikwe and Buvuma districts, Uganda. Methods: A cross-sectional study was conducted involving 162 participants from health centres in Buikwe and Buvuma districts. Stool samples were collected and analyzed in parallel using Kato-Katz microscopy and a newly developed quantitative Real-Time PCR assay. The PCR assay targeted the small-subunit ribosomal RNA (ssrRNA) gene. Diagnostic performance parameters, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and kappa agreement, were calculated.Results: Real-Time PCR detected a significantly higher number of G. intestinalis infections (15/162, 9.3%) compared to Kato-Katz microscopy (5/162, 3.1%). All microscopy-positive samples were also positive by PCR. Using a composite reference standard, Real-Time PCR demonstrated a sensitivity of 75% and a specificity of 100%. The positive and negative predictive values were 100% and 93.6%, respectively. The agreement between the two methods was moderate (kappa = 0.47). The assay showed a high detection limit, capable of identifying as little as 0.1 pg of Giardia DNA. Stool consistency was significantly associated with parasite detection, with watery stools yielding more positives. Conclusion: This study confirms that Real-Time PCR is a substantially more sensitive and reliable tool for diagnosing Giardia intestinalis than Kato-Katz microscopy, particularly in detecting low-level and asymptomatic infections. The findings advocate for the integration of molecular diagnostics into public health strategies in endemic regions to improve disease surveillance, ensure accurate burden estimation, and guide effective control interventions against giardiasis.Keywords: Giardia intestinalis, Giardiasis, Real-Time PCR, Kato-Katz, Diagnostic performance, Buikwe, Buvuma.