Coccidioidomycosis is a fungal infection caused by Coccidioides immitis that is endemic in southwest United States, Mexico, and South America and can cause severe respiratory symptoms and disseminated disease affecting multiple organ systems. (1) Coccidioides infection is diagnosed by serology tests including Enzyme Immunoassay (EIA), Immunodiffusion (ID) and complement fixation (CF). EIA has a high sensitivity, but it can show discrepancies between IgM and IgG test results and has a controversially high risk of false-positives (2). Confirmation with ID and CF is usually required to make the diagnosis, but both assays are complicated, subjective to interpretation, and have to be performed in a reference laboratory (3). With the rising rates for Coccidioidomycosis in the last decade, there is an increasing demand for a simpler but reliable test accessible to local health providers. This is especially important as the disease spreads to non-endemic areas due to global climate change. In this study, we compared the performance of a new Coccidioides Antibody Lateral Flow Assay (Cocci Ab LFA) from Sōna with the existing serology tests and evaluated its potential as an effective screening test for Coccidioides infection for local healthcare providers.
Materials and Methods
Remnant serum samples from patients suspected of having Coccidioidomycosis were collected with standard procedures as done in the clinical setting. Clinical samples were screened by Cocci EIA. A positive EIA sample was confirmed for ID and CF within the UCLA Clinical Microbiology Laboratory. All remnant samples both positive and negative were tested on the Cocci Ab LFA by following the manufacture’s protocol.
Since the incidence of Coccidioidomycosis is low (1-3%), the aim was to collect samples from 1000 remnant patient serum specimens sent to the lab for Cocci serology testing, to obtain a reasonable number of Coccidioides positive samples. The goal was to test at least 100 Cocci EIA positive samples. To date, 458 samples were tested using the Cocci Ab LFA. Among all the patients, 44 (9.6%) were tested EIA positive, and 414 (90.4%) were tested EIA negative. EIA positive samples were followed up with ID and CF.
Result and Conclusion
According to our preliminary data, the Sōna Coccidioides Lateral Flow Assay demonstrated a 94.74% sensitivity (95% CL: 82.25-99.36) and 98.57% specificity (95% CL: 96.2-99.47) when compared to EIA, the current standard screening method. Moreover, with a high negative predictive value of 99.52% (95% CL: 99.52-99.87), the lateral flow assay allows for a rapid 30-minute screen to rule out patients that are suspected of having Coccidioidomycosis, which is critical in the clinical management of these patients. The cost of Cocci Ab LFA may be higher since it cannot be done in bulk as with EIA, but if local clinics has low demand of testing, it may still be a more economical choice.
- Nguyen, C., Barker, B. M., Hoover, S., Nix, D. E., Ampel, N. M., Frelinger, J. A., ... & Galgiani, J. N. (2013). Recent advances in our understanding of the environmental, epidemiological, immunological, and clinical dimensions of coccidioidomycosis. Clinical microbiology reviews, 26(3), 505-525.
- Malo, J., Luraschi-Monjagatta, C., Wolk, D. M., Thompson, R., Hage, C. A., & Knox, K. S. (2014). Update on the diagnosis of pulmonary coccidioidomycosis. Annals of the American Thoracic Society, 11(2), 243-253.2
- Martins, T. B., Jaskowski, T. D., Mouritsen, C. L., & Hill, H. R. (1995). Comparison of commercially available enzyme immunoassay with traditional serological tests for detection of antibodies to Coccidioides immitis. Journal of clinical microbiology, 33(4), 940-943.