Analysis on the influencing factors related to positive detection rate of hand, foot and mouth disease from various specimens in Chaoyang district of Beijing

Objective To compare the positive detection rates of hand, foot and mouth disease (HFMD) from different types of specimen, and to analyze the influencing factors. Methods From October to December 2016, this study was performed in Chaoyang district of Beijing, the positive detection rates were compared between throat swabs and anal swabs. The demographic characteristics, the type of specimen, interval from onset to sampling time, sampling institutions and other relevant information were collected and the influencing factors were explored through standardized residuals, trend x2 and logistic regression analysis. Results A total of 555 pairs of specimens were collected. The positive detection rate of anal swab (78.38%, 435/555) was higher than that of throat swab (61.98%, 344/555; x2=46.79, P<0.01). For Coxsackie virus A16 (CA16) and Coxsackie virus A6 (CA6), anal swab (30.27%, 168/555; 25.41%,141/555) was higher than throat swab (24.68%, 137/555; 3.42%, 19/555; x2=9.33, P<0.01; x2=100.57, P<0.01). For other enterovirus, throat swab (23.06%,128/555) was higher than anal swab (11.53%, 64/555; x2 =26.60, P<0.01). When the positive detection rates in the same interval from onset to sampling, we found that anal swab was higher than throat swab, among them day-2, day-4, day-5, day-6, and day-9 were statistically significant (x2=5.15, P<0.05; x2=9.91, P<0.05; x2=4.12, P<0.05; x2=4.27, P<0.05; x2=4.71, P<0.05). The positive rate decreases with the sampling time delay (anal swab: x2trend=12.91, P<0.01; x2trend=22.49, P<0.01). Logistic regression analysis showed that sampled by town center (OR=0.64, 95%CI 0.47-0.87), anal swab (OR=2.10, 95%CI 1.62-2.71) and the interval from onset to sampling (OR=0.81, 95%CI 0.77-0.85) were influencing factors of the positive detection rate. Conclusions Anal swab was easy to detect Cox A16, Cox A6, throat swab was easy to detect other enterovirus. For HFMD, the earlier samples were collected, the higher positive detection rates were, and at the same interval from onset to sampling time, the anal swab had higher positive detection rate than throat swab. Key words: Hand, foot and mouth disease; Detection rate; Factor analysis