Effects of incubation conditions on results of qualitative ELISA

Objective To determine the effects of incubation temperature time and mode on results of HBsAg by qualitative ELISA.Methods A negative serum sample and a series of sera samples with different HBsAg concentration(0.2,0.5,1.0,2.0,5.0 ng/ml) were tested by using commercial HBsAg ELISA kits under conditions set as follows:incubation time was set for 45,60,75,90 and 120 minutes when incubation temperatures were at 37℃and room temperature(23±1℃).Two incubation modes(static and shaking) were used for room temperature incubation.The times for the incubation set as 45min,1hr,2hrs and 4 hrs.Results With incubation time extended,the S/CO values of the sera with HBsAg increased,especially for weak positive samples.Compared two hours and one hour incubation time,there was a significantly increase in S/CO value of the series of the sera with HBsAg.Moreover,the negative results of the sample with 0.2 ng/ml HBsAg when used one hour incubation changed to positive with two hours incubation.Meanwhile,there was no markedly changes in S/CO values of serum without HBsAg.The S/CO values of the series of sera with HBsAg at room temperature with shaking were much higher than those without shaking.Conclusion The results showed that incubation conditions markedly influences S/CO values of qualitative ELISA,especially on weak positive samples.