Human Serum IgG Antibody Against SARS Coronavirus Tested by 2 ELISA Essay

Objective To observe the positive rate and distribution characteristic of the serum IgG antibody to severe acute respiratory syndrome(SARS)coronavirus among different populations,especially the healthy children aged≤14 years old. Methods This study has confirmed and analyzed the reliability and consistence of 2 enzyme-linked immunosorbent assay(ELISA), and evaluated the practical value of specific IgG testing on SARS diagnosis,by 2 ELISA,utilizing the antigens of resolved fluid of the whole virus (CoV) and the purified N protein respectively test the specific antibody of 70 SARS cases,55 healthy infants aged 3-6ms,297 healthy children aged ≤14 ys and 156 healthy adults aged ≥15 ys.The sensitivity,specificity,positive predictive value (PPV),negative predictive value (NPV) and veracity of the 2 ELISA tests were used to evaluate the utility value on laboratory diagnosis of SARS.Kappa and χ 2 were used to evaluate the consistence and difference between the testing results. Results The results showed that the positive rates tested by ELISA using the whole virus as antigen were 75.71% in SARS cases,36.36% in healthy infants,23.91% in healthy children and 1.92% in healthy adults.The positive rates were 51.16% in 0 age group,41.89% in 1 year old group,30.95% in 2 years old group,18.60% in 3 years old group,16.67% in 4 years old,group 2.38% ( in 5-9 years) old group and 4.76% in 10-14 years old group,respectively.With the increase of age the antibody positive rate showed downtrend.The antibody positive rate tested by ELISA using N protein was 80% in SARS cases and negative in healthy population including all age groups.For people ≥15 years old,the consistence of the results by 2 ELISA methods in measurements of SARS antibodies was very high.The kappa value was 0.881,and there was no significant difference(χ 2=0.10,P0.05). For children ≤14 years old,there was significant difference(χ 2=89.0,P0.005).The sensitivity,specificity,PPV,NPV and veracity of 2 ELISA methods on the diagnosis of SARS were 75.71%,81.50%,36.05%,96.06%,80.80% and 80.00%,100.0%,100.0%,97.32%,97.58%,respectively.There were significant differences on specificity,PPV and veracity. Conclusion The whole virus ELISA test could be used to diagnose the adult SARS whose disease course was above 10 days,but the N protein ELISA test was more specific and more verified which was helpful to diagnose the SARS cases of different age groups,especially the children SARS which is difficulf in identification.This method was widely used to confirm the clinical diagnosis and the serum epidemiological investigation and had important reference value.