Low hepatitis B prevalence among pre-school children in Denmark: Saliva anti-HBc screening in day care centres

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Abstract
Although Denmark has a low hepatitis B virus (HBV) prevalence, HBV transmission has been reported in Danish day‐care centres. The aim of this study was to validate saliva anti‐HBc testing as a method for HBV screening, the applicability of saliva sampling to pre‐school children, and to determine the HBV prevalence in Danish day‐care centres with a high proportion of immigrants. For validation, paired saliva and plasma samples were obtained from blood donors and injecting drug users. Employees and children in day‐care centres with a high proportion of immigrant children were offered saliva screening followed by blood test if positive. The specificity and sensitivity of anti‐HBc tests on saliva was 100% (102 blood donors and four injecting drug users) and 85.9% (61 of 71 anti‐HBc‐positive injecting drug users), respectively. In all samples from HBsAg (n = 7) or anti‐HBc IgM‐positives (n = 9), anti‐HBc was detected in saliva. Adequate saliva samples were obtained from 93% (588/634) of children and 100% (166/166) of employees participating in the day‐care centre survey. Among children 55% were of non‐Scandinavian origin and only one (0.2%, 95% CI [0.0; 1.0]) was HBV positive. Among employees the corresponding values were 22% and 7 (4.2%). The positive predictive value of the saliva test was 25% (1/4) among children and 88% (7/8) among adults. In conclusion, saliva testing is feasible for HBV screening among children in low prevalence populations, but any anti‐HBc reactivity should be confirmed by plasma analysis. The HBV prevalence in pre‐school children in Denmark is low even among immigrants from endemic areas. J. Med. Virol. 68:500–504, 2002.