[Evaluation of various criteria for the interpretation of western blot for the diagnosis of human immunodeficiency virus infection. Spanish Group for the Study of HIV-2].

BACKGROUND

The Western blot (WB) is the most commonly used test to confirm the presence of antibodies against the human immunodeficiency virus type 1 (HIV-1). Different criteria of interpretation of the band profile have been proposed with there being no unanimity as to its reliability. The sensitivity and specificity of several criteria proposed for the interpretation of WB were evaluated and the individual significance of the reactivity of each band of the WB was analyzed.

METHODS

The presence of antibodies against HIV-1 was prospectively studied in 8,073 samples of subjects with risk of infection. A total of 1,993 (25%) were reactive by ELISA and 1,261 were analyzed by WB, with a semiquantitative reading of the bands with a point scale from 0 to 2 being performed. The final interpretation of the WB (negative, doubtful, or positive) was carried out following 5 recommendations of usage. A test designed with synthetic peptides (Pepti-lav) was used as a reference and in discordant cases, other more specific serologic tests and/or genetic analysis by polymerase chain reaction (PCR) were performed.

RESULTS

In order of frequency, the greater sensitivity was found to be for the CRSS (Consortium for Retrovirus Serology Standardization) criteria (97.9%), OMS (96.6%), CDC (Center for Disease Control) (95.9%), ARC (American Red Cross) (95.6%) and FDA (99.8%). The greatest specificity was for the criteria of the OMS, and FDA (99.8%). In order of frequency, the most frequent bands in HIV-1 + individuals were gp160 (99%), gp120, p24, p31, p55, p68, gp41, and p17 (68%). In non infected individuals, the recognized bands were, in decreasing order, p24, p17, p55, p68, p31, and glucoproteins.

CONCLUSIONS

Different criteria of interpretation of the Western blot provide different degrees of sensitivity and specificity. The Western blot is a non standardized, expensive, laborious technique of subjective interpretation which provides an appreciable number of undetermined results.