A robust dry reagent lateral flow assay for diagnosis of active schistosomiasis by detection of Schistosoma circulating anodic antigen

Abstract

An earlier reported laboratory assay, performed in The Netherlands, to diagnose Schistosoma infections by detection of the parasite antigen CAA in serum was converted to a more user-friendly format with dry reagents. The improved assay requires less equipment and allows storage and worldwide shipping at ambient temperature. Evaluation of the new assay format was carried out by local staff at Ampath Laboratories, South Africa. The lateral flow (LF) based assay utilized fluorescent ultrasensitive up-converting phosphor (UCP) reporter particles, to be read by a portable reader (UPlink) that was also provided to the laboratory. Over a period of 18 months, about 2000 clinical samples were analyzed prospectively in parallel with a routinely carried out CAA-ELISA. LF test results and ELISA data correlated very well at CAA concentrations above 300 pg/mL serum. At lower concentrations the UCP-LF test indicates a better performance than the ELISA. The UCP-LF strips can be stored as a permanent record as the UCP label does not fade. At the end of the 18 months testing period, LF strips were shipped back to The Netherlands where scan results obtained in South Africa were validated with different UCP scanning equipment including a novel, custom developed, small lightweight UCP strip reader (UCP-Quant), well suited for testing in low resource settings. Conclusion The dry format UCP-LF assay was shown to provide a robust and easy to use format for rapid testing of CAA antigen in serum. It performed at least as good as the ELISA with respect to sensitivity and specificity, and was found to be superior with respect to speed and simplicity of use. Worldwide shipping at ambient temperature of the assay reagents, and the availability of small scanners to analyze the CAA UCP-LF strip, are two major steps towards point-of-care (POC) applications in remote and resource poor environments to accurately identify low (30 pg CAA/mL serum; equivalent to about 10 worm pairs) to heavy Schistosoma infections.

Advances in the Diagnosis of Human Schistosomiasis

“…Some recent advances in the detection of circulating schistosomal antigen have involved UCP-LF (165,193,194), as described above. Detection of an active, single-species worm infection by using different clinical samples in a UCP-LF CAA assay has been shown to be possible, although further technical improvements will be needed to make it convenient and field applicable (165).…”

Real-Time Polymerase Chain Reaction for Detection of Schistosoma DNA in Small-Volume Urine Samples Reflects Focal Distribution of Urogenital Schistosomiasis in Primary School Girls in KwaZulu Natal, South Africa

“…Based on this knowledge, there is also a clear need for a rapid and field applicable diagnostic test to allocate these hot spots in resource-poor settings without the need of high technology laboratory equipment. 33,34 In conclusion, our findings illustrate that the diagnostic potentials of urine Schistosoma real-time PCR is dependent on the quality and intensity of performed microscopy. Repeated microscopy may in certain settings be more sensitive but at the same time it is a highly laborious as well as observer dependent procedure.…”

Longitudinal IP-10 Serum Levels Are Associated with the Course of Disease Activity and Remission in Patients with Rheumatoid Arthritis

“…Moreover, the user-friendly UCP-LFA can also be combined with finger-stick blood instead of serum derived from venous blood (27). This allows (self-)monitoring of IP-10 levels as well as other relevant markers in blood that are indicative of DMARD-free remission.…”