From the Guidelines
Schistosomiasis diagnosis should involve a combination of microscopic examination of stool or urine samples, serological tests, and point-of-care tests, with the circulating cathodic antigen (CCA) test being particularly effective for Schistosoma mansoni, as evidenced by recent studies 1. The diagnosis of schistosomiasis typically involves microscopic examination of stool or urine samples to detect parasite eggs, which remains the gold standard test. For intestinal schistosomiasis, stool samples are examined using the Kato-Katz technique, while urinary schistosomiasis requires urine filtration to identify eggs. Multiple samples collected on different days improve detection rates. Some key points to consider in the diagnosis of schistosomiasis include:
- Serological tests like ELISA detect antibodies against schistosome antigens and are useful for diagnosing infections in travelers or in low-endemic areas, though they cannot distinguish between current and past infections 1.
- Point-of-care tests include the circulating cathodic antigen (CCA) test using urine samples, which is particularly effective for Schistosoma mansoni 1.
- PCR-based molecular tests offer high sensitivity but are mainly used in research settings due to cost and technical requirements.
- In non-endemic regions where egg output may be low, a combination of microscopy and serological testing is recommended.
- Imaging techniques like ultrasound can help assess complications such as liver fibrosis or bladder pathology in chronic cases. It is essential to note that the choice of diagnostic test may depend on the specific species of schistosome, the level of endemicity, and the individual patient's symptoms and history. Recent studies have highlighted the importance of using more sensitive assays, such as the CCA test, to detect schistosomiasis, especially in areas with low prevalence 1. Overall, a comprehensive approach to diagnosis, taking into account the strengths and limitations of each test, is crucial for accurate diagnosis and effective management of schistosomiasis.
From the Research
Diagnostic Tests for Schistosomiasis
The diagnostic tests for schistosomiasis (bilharzia) include:
- Microscopic detection of eggs of the parasite in the stool, which is the most widely used tool for the actual diagnosis of active infection 2
- Kato-Katz technique, a coproscopic method that has the advantages of higher sensitivity, the possibility of egg quantification, its low operational cost, and its feasibility in areas with minimal infrastructure 2, 3, 4
- Rectal biopsy, which is valuable in initial clinical trials of schistosomicides and can be an alternative method for individual diagnosis, being more sensitive than a single stool exam in low-intensity infection 2
- Saline gradient method and the Helmintex(®) method, which were found to be more effective in diagnosing schistosomiasis mansoni in a low endemic area compared to the Kato-Katz method 5
- Urine point-of-care circulating cathodic antigen test (POC-CCA), which is potentially more sensitive than the Kato-Katz method, especially after repeated praziquantel treatments 4
- Dipstick dye immunoassay (DDIA), fast enzyme-linked immunosorbent assay (F-ELISA), indirect haemagglutination test A (IHA-A) and B (IHA-B), which are sero-diagnostics with varying sensitivity and specificity 6
Comparison of Diagnostic Tests
The sensitivity and specificity of these diagnostic tests vary, with:
- Kato-Katz method having a sensitivity of 98.6% and specificity of 100% 4
- POC-CCA having a sensitivity of 91.7% and specificity of 75.0% 4
- DDIA, F-ELISA, IHA-A, and IHA-B having sensitivity and specificity lower than 90% 6
- Saline gradient method and the Helmintex(®) method being more effective than the Kato-Katz method in a low endemic area 5
Recommendations for Diagnostic Tests
The choice of diagnostic test depends on the specific context and purpose, with:
- Kato-Katz method being recommended for field diagnosis of intestinal schistosomiasis 3
- POC-CCA being recommended for monitoring and evaluation (M&E) and drug-efficacy studies 4
- A combination of multiple diagnostic tests being recommended to improve the diagnosis of schistosomiasis mansoni in low endemic settings 5