Validation of a New Test for Schistosoma haematobium Based on Detection of Dra1 DNA Fragments in Urine: Evaluation through Latent Class Analysis

Abstract

BackgroundDiagnosis of urogenital schistosomiasis in chronically infected adults is challenging but important, especially because long term infection of the bladder and urinary tract can have dire consequences. We evaluated three tests for viable infection: detection of parasite specific DNA Dra1 fragments, haematuria and presence of parasite eggs for sensitivity (Se) and specificity (Sp).MethodsOver 400 urine specimens collected from adult volunteers in an endemic area in Western Nigeria were assessed for haematuria then filtered in the field, the filter papers dried and later examined for eggs and DNA. The results were stratified according to sex and age and subjected to Latent Class analysis.ConclusionsPresence of Dra1 in males (Se = 100%; Sp = 100%) exceeded haematuria (Se = 87.6%: Sp = 34.7%) and detection of eggs (Se = 70.1%; Sp = 100%). In females presence of Dra1 was Se = 100%: Sp = 100%, exceeding haematuria (Se = 86.7%: Sp = 77.0%) and eggs (Se = 70.1%; Sp = 100%). Dra1 became undetectable 2 weeks after praziquantel treatment. We conclude detection of Dra1 fragment is a definitive test for the presence of Schistosoma haematobium infection.

Impact of Short-Time Urine Freezing on the Sensitivity of an Established Schistosoma Real-Time PCR Assay

“…14 Freezing of urine or the pellet from concentrated urine did not show a negative effect on the amplification of Schistosoma-specific DNA as found by others. 18 On the contrary, in this study freezing increased the number of PCRpositive samples suggesting that freezing resulted in a more successful DNA release.…”

“…5,[11][12][13][14] In this study, we are assessing the effect of concentration by centrifugation and frozen storage of urine samples on the sensitivity of a Schistosoma real-time PCR assay routinely used in our laboratory.…”

Molecular Diagnosis of Schistosoma Infections in Urine Samples of School Children in Ghana

“…Although it is not clear why Schistosoma DNA could not be amplified in seven of the microscopy positive samples (1-12 eggs/10 mL) apparently Schistosoma DNA, sometimes with high DNA loads, can be present even in the absence of eggs in the urine sample. A higher sensitivity of the PCR in samples with low egg counts might be achievable by using a larger volume of the urine sample by applying filter-based DNA isolation methods 16,17 In the schools included in this study, the higher sensitivity of the real-time PCR results in much higher negative predictive values ( 94.6%) as compared with microscopy (54.3-95.7%).…”

Molecular Testing for Clinical Diagnosis and Epidemiological Investigations of Intestinal Parasitic Infections

“…A higher sensitivity of PCR in samples with low egg counts might be achieved by the use of larger volumes of urine samples and filterbased DNA isolation methods (390)(391)(392)(393). Latent class analysis of hematuria, microscopy, and PCR targeting the S. haematobiumspecific DraI repeat sequence using DNA isolated from one-quarter of a filter paper after filtration of 50 ml of urine showed sensitivities of 87%, 70%, and 100%, respectively (392). ten Hove et al…”