Circulating antigen tests and urine reagent strips for diagnosis of active schistosomiasis in endemic areas

Abstract

How well do point-of-care tests detect Schistosoma infections in people living in endemic areas?

Schistosomiasis, also known as bilharzia, is a parasitic disease common in the tropical and subtropics. Point-of-care tests and urine reagent strip tests are quicker and easier to use than microscopy. We estimate how well these point-of-care tests are able to detect schistosomiasis infections compared with microscopy.

We searched for studies published in any language up to 30 June 2014, and we considered the study’s risk of providing biased results.

What do the results say?

We included 90 studies involving almost 200,000 people, with 88 of these studies carried out in Africa in field settings. Study design and conduct were poorly reported against current expectations. Based on our statistical model, we found:

  • Among the urine strips for detecting urinary schistosomiasis, the strips for detecting blood were better than those detecting protein or white cells (sensitivity and specificity for blood 75% and 87%; for protein 61% and 82%; and for white cells 58% and 61%, respectively).
  • For urinary schistosomiasis, the parasite antigen test performance was worse (sensitivity, 39% and specificity, 78%) than urine strips for detecting blood.
  • For intestinal schistosomiasis, the parasite antigen urine test, detected many infections identified by microscopy but wrongly labelled many uninfected people as sick (sensitivity, 89% and specificity, 55%).

What are the consequences of using these tests?

If we take 1000 people, of which 410 have urinary schistosomiasis on microscopy testing, then using the strip detecting blood in the urine would misclassify 77 uninfected people as infected, and thus may receive unnecessary treatment; and it would wrongly classify 102 infected people as uninfected, who thus may not receive treatment.

If we take 1000 people, of which 360 have intestinal schistosomiasis on microscopy testing, then the antigen test would misclassify 288 uninfected people as infected. These people may be given unnecessary treatment. This test also would wrongly classify 40 infected people as uninfected who thus may not receive treatment.

Conclusion of review

For urinary schistosomiasis, the urine strip for detecting blood leads to some infected people being missed and some non-infected people being diagnosed with the condition, but is better than the protein or white cell tests. The parasite antigen test is not accurate.

For intestinal schistosomiasis, the parasite antigen urine test classifies many microscopy negative people as being infected. This finding may be explained by the low sensitivity of microscopy.

Citation

Ochodo, E.A.; Gopalakrishna, G.; Spek, B.; Reitsma, J.B.; van Lieshout, L.; Polman, K.; Lamberton, P.; Bossuyt, P.M.M.; Leeflang, M.M.G. Circulating antigen tests and urine reagent strips for diagnosis of active schistosomiasis in endemic areas. Cochrane Database of Systematic Reviews (2015) : CD009579. [DOI: 10.1002/14651858.CD009579.pub2]

Circulating antigen tests and urine reagent strips for diagnosis of active schistosomiasis in endemic areas

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