Detection of HIV-1 antibodies in blood specimens spotted on filter-paper.

Described are the results of an international collaborative study to evaluate th e use of the whole blood samples spotted on filter-paper (BSP) for the detection of antibodies to human i mmunodeficiency virus type 1 (HIV-1). BSP samples were collected from 40 patients at risk for HIV-1 in fection and tested blindly using commercially available HIV antibody test kits, either specifically manufactured or modified for this purpose. Parallel serum samples were also collected, and the antibody r eactivity was defined and confirmed by Western blot. The results demonstrate that recovery of antibodies from BSP samples after elu tion can be comparable to that from serum. Some kits can be easily adapted to test BSP samples, while o thers cannot. At present, detection of HIV antibodies in BSP samples should therefore be carried out using kits specifically manufactured for this purpose or by the development of a modified protocol using a panel of BSP and their corresponding serum specimens. Introduction The identification of human immunodeficiency virus (HIV) infection is mainly based on the detection of specific antibodies to viral antigens in samples of serum or plasma[1]. Although much progress has been made in developing diagnostic reagents, antibody reactivity still requires confirmation; multiple samples are therefore often needed to complete testing[2]. Epidemiological studies can be hampered by the difficulty in obtaining adequate samples of blood, particularly from infants or elderly patients, and storage of aliquots may be difficult in developing countries. In the last 20 years newborns have been screened for metabolic disorders by testing blood spotted on filter-paper (BSP)[3]. This method has also been used to diagnose several diseases, such as measles (4), viral hepatitis B[5], and, more recently, to detect antibodies to HIV[6-11]. The collection of whole blood on filter-paper for antibody assay has unique advantages over the use of serum samples. Equipment requirements are minimal - inexpensive sterile lancets and filter-papers replace the syringes, tubes, centrifuges, refrigerators, and freezers that are needed for serum collection and sto-rage. The filter-cards used are light, hold up to eight aliquots, cannot be broken or spilt, can be stored at room temperature for several weeks, require minimal storage space, and can be sent by mail. The BSP technique is therefore particularly suitable for use in screening programmes in developing countries. Use of the BSP technique to screen for HIV antibodies needs to be validated to verify whether the results obtained in different assays are comparable to those obtained by analysis of serum or plasma. The present international collaborative study therefore assessed the usefulness of different HIV antibody assays of BSP samples, using a panel of 40 paired samples of BSP and the corresponding serum samples. Methods Specimens Forty blood samples (10 ml each) were collected in 1989-90 by venepuncture using heparinized syringes from patients (25 intravenous drug addicts, 11 sexual partners of HIV-1 positive subjects, and 4 homosexual males) who were attending the Clinic of Infectious Diseases, Genoa. Whole blood was spotted slowly to avoid splashing and to saturate the filter-paper (Schleicher & Schull, grade 903) until blood was visible on the reverse side of the test card and filled the delineated circle of 1-cm diameter (about 250 [mu]l per spot). It was not possible to collect the samples by finger-stick because of the need to prepare several spotted test cards (6 coded cards with 8 BSP each) to distribute to the three collaborating laboratories. The cards were kept at room temperature until the blood had dried, stored in sealed plastic bags, and sent to the laboratories wrapped in double plastic envelopes that were placed in a box marked "biohazard". Serum was separated from the blood samples and stored frozen until tested at the Institute of Microbiology, Genoa. …