[Evaluation of four kits for screening HIV antibody]

To Evaluate four kits for screening HIV antibody by comparing and analyzing the HIV antibody screening positive results and Western Blot (WB) test results.

From January 2004 to June 2009, three ELISA kits (Zhongshan, Biomérieux and Livzon) were used for initial screening HIV antibody. The reactive positive samples were reexamed by initial ELISA kit and a rapid kit (Abbot Determine HIV-1/2). All repeatedly reactive positive screening results were followed by WB test.

A total of 193 (0.094%) WB confirmed positive results were obtained from 206 151 specimens. The sensitivities and predictive values of negative test result (PVN) of three ELISA kits were all 100% and those of Abbot Determine HIV-1/2 were 93.93%, and 91.67% respectively. All false negative results from Abbot were WB indeterminate. The specificities of Zhongshan, Biomérieux, Livzon and Abbot were 99.88%, 99.89%, 99.96% and 89.38%; the study predictive values of a positive test result (PVP) were 35.58%, 46.46%, 76.61% and 92.20%; the efficiencies were 99.88%, 99.89%, 99.96% and 91.98%; the areas under ROC curve of the three ELISA kits were 0.93, 0.99, and 0.95 respectively. PVP of Livzon was obviously higher than those of Zhongshan (chi(2) = 45.804, P = 0.000), Biomérieux (chi(2) = 25.231, P = 0.000) and Biomérieux was higher than Zhongshan (chi(2) = 2.488, P = 0.115). PVP of Abbot was highest (chi(2) = 18.633, P = 0.000, vs Livzon). There were some specimens with S/CO (optical density of sample/cut off) ratio < 6 or > or = 6 in all three groups with positive, indeterminate and negative WB results. The S/CO ratio from Zhongshan in confirmed positive group (14.29 + or - 2.63) was higher than in positive-negative group (2.80 + or - 3.25) (t = 17.652, P = 0.000). The S/CO ratio from Biomérieux in confirmed positive group(16.09 + or - 2.35) was higher than in positive-negative group (2.14 + or - 1.91) (t = 31.622, P = 0.000). The S/CO ratio from Livzon in confirmed positive group (11.54 + or - 1.95) was higher than in positive-indeterminate group (5.54 + or - 3.57) (t = 6.386, P = 0.000), positive-negative group (3.25 + or - 2.41) (t = 21.772, P = 0.000) and positive-indeterminate group was higher than positive-negative group (t = 2.301, P = 0.033).

The performances of four HIV antibody screening kits are good but estimating WB confirming result in line with S/CO ratio is not available. All repeated screening positive results should be followed by confirmatory tests.