Molecular and Serological Diagnosis of Strongyloides stercoralis Infection Among Cancer Patients at Hospital Universiti Sains Malaysia

Strongyloidiasis, caused by Strongyloides stercoralis, is a neglected disease with a worldwide prevalence, particularly in tropical and subtropical regions. Most people have chronic asymptomatic infections, which may transform into potentially fatal hyper- or disseminated infections when immunosuppressed. Cancer patients on corticosteroids are at an increased risk of developing severe forms of the infection due to their impaired immune status. The present study used molecular, serological, and parasitological methods to detect S. stercoralis infection in cancer patients on corticosteroids. Using faecal and serum samples from 99 individuals, real-time PCR demonstrated the highest detection rate (27.3%), followed by the Strongyloides IgG4 rapid test (IgG4-RDT or SsRapid) (22.2%) and a commercial IgG-ELISA (4.0%). Agar plate culture performed on 88 of 99 stool samples was negative. There was no significant difference in detection prevalence between the IgG4-RDT and real-time PCR (p = 0.413), and the agreement between them was slight (kappa coefficient, 0.108). Using a composite reference standard (CRS), 41 of 99 samples (41.4%) were classified as positive for Strongyloides infection. Based on the CRS, PCR demonstrated higher sensitivity (65.9%) than IgG4-RDT (53.7%), while both assays exhibited 100% specificity and positive predictive value (PPV). The negative predictive value (NPV) was greater for PCR (80.6%) than IgG4-RDT (75.3%). McNemar's test indicated no significant difference between the two assays (p = 0.49). Notably, combining results of the real-time PCR and IgG4-RDT increased the detection rate to 41%, which was significantly higher than that of PCR alone (27%, p = 0.036) or IgG4-RDT alone (22%, p = 0.0036). The combined results showed substantial agreement with PCR (k = 0.693) and moderate agreement with IgG4-RDT (k = 0.576). In conclusion, the combination of real-time PCR and IgG4-RDT offers a more reliable approach for detecting S. stercoralis in cancer patients undergoing corticosteroid therapy than either assay alone.