No evidence of over-reporting of SARS in mainland China.

Summary objective To find out whether there was over-reporting of SARS patients in mainland China in view ofthe relatively low case fatality ratio in mainland China, in comparison with other affected countries andareas.methods We searched PubMed for all SARS antibody detection papers (in English or Chinese lan-guage) using the keywords ‘SARS’ and ‘antibody’. Then the resulting articles were further read throughto select the SARS detection results using ELISA methods of serum samples collected at least 1 monthafter disease onset. A multi-level logistic regression was applied to test for possible differences in theproportions positive between locations of the study.results A total of 48 studies were identified, including 39 from mainland China and nine fromelsewhere (Hong Kong, Taiwan, Canada and Vietnam). For mainland China, there was no differencebetween Guangdong, Beijing and other provinces in the proportions testing positive (83.0%, 85.8% and85.4% respectively). The grand average of 84.2% seropositive was lower than the 95.1% for thecountries and areas outside of mainland China combined. However, this difference was far from sig-nificant 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 inGuangdong, 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 amodest 10% of the lower case fatality in mainland China.keywords SARS, over-reporting, serologyIntroductionThe worldwide outbreak of severe acute respiratorysyndrome (SARS) struck mainland China, as well as HongKong, Taiwan, Singapore, Vietnam, Canada and eventu-ally 32 countries or regions (WHO 2003). In mainlandChina, a total of 5327 cases had been diagnosed asprobable SARS according to the definition for clinicallyconfirmed SARS issued by the Ministry of Health ofPeople’s Republic of China in 2003 (Feng et al. 2009; thisissue), of which 343 eventually died. The WHO reportsshowed that the case fatality ratio of 6.4% in mainlandChina was considerably lower than in other affectedcountries and areas, such as Hong Kong and Toronto,where the case fatality ratio was about 17% (Feng et al.2009; this issue). It has been suggested that over-reportingmay have played a role in mainland China, especiallyduring the earliest stage of the epidemic in Guangdongwhen SARS was largely unknown. Chen et al. (2006) madea follow-up survey of seroconversion in more than 1000convalescent SARS patients in Guangzhou (GuangdongProvince). They found that 30% of the ‘SARS’ patientswere SARS IgG serum negative. In other words, only 70%of ‘SARS’ patients could eventually be confirmed and theothers may have been the result of over-reporting. The casefatality in Guangdong would change from 3.8% (Jia et al.2009, this issue) to 4.7% after removing these possiblyfalse-positive patients, which is still far lower than those inother affected countries or regions.It remains a much-debated issue whether there was aproblem of over-reporting of SARS patients in Guangdongor other parts of mainland China. Most of the previousreports used clinically oriented criteria for case identifica-tion, which was not specific and certainly to some extentprone to over-diagnosis. A definite diagnosis of SARS canonly be made for those who have shown positive serumSARS IgG antibody, i.e. a fourfold rise in serum SARS-IgGthat will last 2 years in convalescent patients (Liu et al.2006). So the evaluation and comparison based on theserological antibody positive rates among various epidemic