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

Urogenital schistosomiaisis is a serious public health problem in sub-Saharan Africa. In this study, we have updated an established real-time polymerase chain reaction (PCR) routinely used in our laboratory. Schistosoma genus- specific real-time PCR was performed on DNA isolated from 85 urine samples and pellets obtained after centrifugation without and after frozen storage. The results revealed that concentration by centrifugation of the urine samples and freezing of the samples before extracting DNA improves the sensitivity of the PCR. Urogenital schistosomiasis is a chronic disease acquired in early childhood or in adulthood. In Africa, an estimated 120 million people are infected with Schistosoma haematobium, the etiologic agent. 1 Untreated infections can lead to serious complications such as liver and bladder cancer, kidney failure, and infertility. Moreover, lesions of the vagina and cervix make females more vulnerable to sexually transmitted diseases, espe- cially to human immunodeficiency virus (HIV). 2-4 Therefore, it is critical that the diagnosis of urogenital schistomiaisis be done early using specific and sensitive methods. Urine filtration, the gold standard method has a limited sensitivity in areas of low endemicity or detection of prepatent infections. 5,6 Other diag- nostic tools such as immunodiagnostic assays are sensitive but not very specific, and do cross-react with other helminth infec- tions. 7,8 Moreover, these assays cannot distinguish life parasite from dead parasite as antibodies raised against the antigen crude extracts used in these assays (adult worm antigen and soluble egg antigen ) persist for several months even after successful treatment. 9,10 Molecular approaches like real-time polymerase chain reaction (PCR) and loop-mediated isother- mal amplification are increasingly used for the detection of