Diagnostic Performance of Schistosoma Real-Time PCR in Urine Samples from Kenyan Children Infected with Schistosoma haematobium: Day-to-day Variation and Follow-up after Praziquantel Treatment

Abstract

BackgroundIn an effort to enhance accuracy of diagnosis of Schistosoma haematobium, this study explores day-to-day variability and diagnostic performance of real-time PCR for detection and quantification of Schistosoma DNA compared to other diagnostic tools in an endemic area before and after treatment.MethodologyPreviously collected urine samples (N = 390) from 114 preselected proven parasitological and/or clinical S. haematobium positive Kenyan schoolchildren were analyzed by a Schistosoma internal transcribed spacer-based real-time PCR after 14 years of storage. Pre-treatment day-to-day fluctuations of PCR and microscopy over three consecutive days were measured for 24 children using intra-class correlation coefficient. A combined ‘gold standard’ (PCR and/or microscopy positive) was used to measure sensitivity and negative predictive value (NPV) of several diagnostic tools at baseline, two and 18 months post-treatment with praziquantel.Principal FindingsAll 24 repeatedly tested children were PCR-positive over three days with little daily variation in median Ct-values, while 83.3% were found to be egg-positive for S. haematobium at day 1 and 75.0% at day 2 and 3 pre-treatment, signifying daily fluctuations in microscopy diagnosis. Of all 114 preselected schoolchildren, repeated microscopic measurements were required to detect 96.5% versus 100% of positive pre-treatment cases by single PCR. At two months post-treatment, microscopy and PCR detected 22.8% versus 69.3% positive children, respectively. Based on the ‘gold standard’, PCR showed high sensitivity (>92%) as compared to >31% sensitivity for microscopy, both pre- and post-treatment.Conclusions/SignificanceDetection and quantification of Schistosoma DNA in urine by real-time PCR was shown to be a powerful and specific diagnostic tool for detection of S. haematobium infections, with less day-to-day variation and higher sensitivity compared to microscopy. The superior performance of PCR before, and two and 18 months post-treatment provides a compelling argument for PCR as an accurate and reproducible tool for monitoring treatment efficacy.

New diagnostic tools in schistosomiasis

“…Infection intensity is expressed as the number of eggs per 10 mL of urine with a threshold of 50 eggs distinguishing between light and heavy infection [34]. Although this method is easy to perform, it lacks sensitivity to detect very light infection intensities and is affected by day-to-day variation in egg output [60][61][62]. Hence, to accurately detect light infections, multiple filtrations over consecutive days are needed.…”

Sterile Pyuria

“…* The information is based on Wise, 31 Vinkeles Melchers et al, 34 guidelines from the Centers for Disease Control and Prevention, 42,43 and Shipitsyna et al 44 HIV denotes human immunodeficiency virus, and PCR polymerase chain reaction. or exposure to a high concentration of bird excrement).…”

“…33 An estimated 119 million people in the world are infected with Schistosoma haematobium. 34 Transmission requires the contamination of water by egg-containing feces or urine, a specific freshwater snail as intermediate host, and human contact with water inhabited by the intermediate host snails. 35 The urogenital system is affected in 75% of infected persons.…”

“…A recent study showed that real-time PCR has 100% sensitivity as an indicator of infection intensity. 34 In a 10-year study involving more than 25,000 ill travelers from endemic areas, 410 cases of schistosomiasis were identified; 83% of the infections were acquired in Africa. A total of 63% of the patients with schistosomiasis presented within 6 months after travel.…”

Schistosomiasis – Updating Technologies and Diagnostic Approaches in Surveillance Strategies and Clinical Management

“…The accurate assessment of schistosomiasis diagnosis, morbidity determination, and therapy response through new technologies became suitable for use in both institutional as well as community settings. The upgrade of diagnostic technology that encompasses the detection of active infection before chemotherapy and monitoring of treatment response will permit advances in public health policies as well as in individual clinical management [14,15]. Moreover, the assessment of clinical presentation, the disease stage, and the prognosis have been the object of progresses that go side by side with the development of new image diagnostic apparatus.…”