The Context of HIV Risk Among Drug Users and Their Sexual Partners

FORENSIC TECHNIQUES TO DOCUMENT SELF-REPORTS OF
NEEDLE SHARING
The authors attempted to verify self-reported needle sharing by
performing forensic tests on syringes provided by drug users to determine
whether the tests corroborated what drug users reported they had done
with the syringes (Gibson et al. 1991).
A convenience sample was recruited in a San Francisco street setting and
asked to provide syringes for an anonymous study of injection
equipment. Fifty-nine drug users presented an average of 1.7 syringes for
inspection, with 31 presenting at least one syringe containing visible
blood. With each drug user, a staff member selected a single syringe as
the basis for a brief interview concerning its use by the donor and others,
After completing the 10-item interview, drug users provided a reference
fingerstick blood specimen and were paid $10 for their time. They were
not told of the specific purpose of the study.
Blood residue in the syringes was analyzed for genetic traits using tests
for the isoenzyme phosphoglumatase (PGM), Gamma marker (Gm) and
Kappa marker (Km) immunoglobulin, and HLA-DQ alpha-type. Of the
31 syringes, 27 contained sufficient blood to conduct one or more of the
tests. Genetic markers were obtained in 10 PGM tests, 23 Gm tests,
25 Km tests, and 23 DQ-alpha tests. The reference blood samples
provided by the donors of the 27 syringes were analyzed to determine the
genetic traits of the donors.
In only four syringes were there genetic traits of two drug users. The
analysis indicated, however, that 15 of the 27 syringes had been used by
someone other than the donor. Table 4 shows a cross-tabulation of the
laboratory results with self-report of sharing a dirty needle (i.e., a needle
that had been used by someone else). The table indicates a reasonable
degree of agreement between the laboratory results and self-reports, with
there being a correspondence in 20 of 27 cases (74 percent). However,
more than a third (6 out of 17) of drug users who denied sharing were
contradicted by the laboratory tests. Moreover, in six of the seven cases
where there was a discrepancy between the lab test and self-report, the
drug user denied that he or she had borrowed. Self-reports of needle
sharing thus appear to understate “true” levels of sharing.
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