No evidence of over-reporting of SARS in mainland China

Objective
To find out whether there was over-reporting of SARS patients in mainland China in view of the relatively low case fatality ratio in mainland China, in comparison with other affected countries and areas.
Methods
We searched PubMed for all SARS antibody detection papers (in English or Chinese language) using the keywords 'SARS' and 'antibody'. Then the resulting articles were further read through to select the SARS detection results using ELISA methods of serum samples collected at least 1 month after disease onset. A multi-level logistic regression was applied to test for possible differences in the proportions positive between locations of the study.
Results
A total of 48 studies were identified, including 39 from mainland China and nine from elsewhere (Hong Kong, Taiwan, Canada and Vietnam). For mainland China, there was no difference between Guangdong, Beijing and other provinces in the proportions testing positive (83.0%, 85.8% and 85.4% respectively). The grand average of 84.2% seropositive was lower than the 95.1% for the countries and areas outside of mainland China combined. However, this difference was far from significant after correcting for dependency of individual tests within the same study.
Conclusions
Our study showed no evidence of over-reporting of SARS in mainland China, nor in Guangdong, where the SARS epidemic started. Even if the lower seroprevalence in mainland China, relative to other affected areas, does represent actual over-reporting, then this factor can only explain a modest 10% of the lower case fatality in mainland China.