Detection of HCV antibodies in oral fluid
Introduction
Although conventionally the detection of antibodies is carried out on serum, the collection of blood by venepuncture is invasive, painful and expensive. However, numerous studies have already demonstrated the suitability of oral fluid as an alternative medium for detection of antibodies to several viruses, such as hepatitis A, B and C, HIV, Epstein Barr, parvovirus B19, measles, mumps and rubella (Parry, 1993, Bello et al., 1998, Sherman et al., 1994, Archibald et al., 1986, Connell et al., 1993, Vyse et al., 1997, Rice and Cohen, 1996). The collection of oral fluid samples using a collection device is safe, cheap and simple (Mortimer and Parry, 1991). The immunoglobulin classes and specificities of antibody found in plasma are reflected closely in the gingival crevicular fluid (Parry et al., 1987, Mortimer and Parry, 1988). This gingival crevicular fluid is the oral fluid which transudes from the capillary bed situated beneath the margin between the tooth and the gum (Jenkins, 1978). The concentration of IgG in this gingival crevicular fluid is about 1/800 that of serum (Parry et al., 1987).
Previous studies detecting HCV antibodies in oral fluid resulted in a sensitivity of 87.0 and 84.1% and a specificity of 100.0 and 100.0% using the Orasure collection device with the Ortho HCV 3.0 assay (Allwright et al., 2000, Judd et al., 2003), a sensitivity of 98.2 and 90.0% and a specificity of 99.1 and 100.0% using Abbott Laboratories HCV 2.0 with the Orasure collection device and whole saliva respectively (Sherman et al., 1994, Elsana et al., 2001) and using the Salivette collection device a sensitivity and a specificity of 94.4 and 99.1%, respectively with Abbott HCV 3.0 (Bello et al., 1998) and a sensitivity and a specificity of 85.0 and 100.0%, respectively with Monolisa (Cameron et al., 1999).
The Oracol collection device (Malvern Medical Development, UK) is specifically designed to target the gums providing a better sample quality for antibody testing. It has been demonstrated that this device provided oral fluid samples containing the highest geometric mean concentrations of both total IgG and IgM (Vyse et al., 2001). It also minimizes contamination with sputum, which interferes with serodiagnosis (Major et al., 1991). Using oral fluid for the detection of HCV antibodies could be a useful tool for epidemiological purposes, especially when blood collection is difficult (small children, injecting drug users, haemophiliacs) or for field collection of samples in developing countries or in nonclinical settings by persons with minimal training. Although reliable tests to detect HCV antibodies in serum are used widely, assays for testing oral fluid are not available commercially at present.
This study was conducted to evaluate the detection of HCV antibodies in oral fluid against the detection on serum as the golden standard. In order to do so, 146 paired serum/oral fluid samples were tested, using a modification of a commercial assay.
Section snippets
Study population
The study population included 73 anti-HCV seropositive and 73 anti-HCV seronegative samples. The formula described by Greiner and Gardner (2000) was used for the sample size calculation. The samples were drawn from patients visiting the gastroenterology service (HCV seropositive and HCV seronegative) or other services (HCV seronegative) in the academic hospitals at Antwerp, Brussels and Ghent. The mean age of the patients was 47.5 years (range: 17–84 years), 52.7% was male and 32 of the 73 HCV
Results
Seventy-one of the 73 HCV seronegative oral fluid samples were positive for total IgG quantitation (97.3%). The two IgG negative samples were excluded from the study and replaced by two samples found IgG positive from other patients.
The modifications of the screening assay for optimal HCV antibody detection obtained by preliminary results were the following: A ratio sample/diluent of 1/2, a primary incubation (sample incubation) overnight (i.e. 16 h) at room temperature and a secondary
Discussion
In this study, a striking concordance was found between serum and oral fluid samples for the detection of HCV antibodies with the modified Ortho HCV 3.0 ELISA. Salivary HCV antibodies are detected with a sensitivity and a specificity of 83.6% (95% CI: 72.7–90.9%) and 100.0% (95% CI: 93.8–100.0%), respectively. By lowering the cut-off point 20%, the sensitivity was increased to 89.0% (95% CI: 79.0–94.8%) while the specificity remained 100.0% (95% CI: 93.8–100.0%). These results suggested that
Acknowledgements
We thank all nurses who collected blood and oral fluid at the hospitals and Eric Mairiaux for compiling the statistics. This project was funded by a grant from the Flemish Community.
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