| From: |
joya banerjee [ profile ] |
| Subject: |
Fwd: [GYCA] NYTimes: Contraceptive Used in Africa May Double Risk of H.I.V.
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| Sent: |
Oct 17th, 2011 - 18:14:04 |
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Thanks Guffran for this excellent analysis of the study and its
potential pitfalls. I didn't realize the sample of women on injectable
contraceptives was so small (196.6 person years, or 11% of total
person years of follow up included in the study).
http://www.rhrealitycheck.org/blog/2011/10/04/hormonal-contraceptives-weighing-evidence-weighing-risks
Excerpt:
[S]imilar to all observational studies, this study was open to
aetiological pitfalls. Potential selection bias and confounding could
have distorted interpretation. Furthermore, like all but two studies
on this topic, this study was a secondary analysis of an
HIV-prevention trialnot specifically designed to examine hormonal
contraception and HIV risk. Few women used hormonal contraceptives
(only 196.6 [11%] of the total person-years of follow-up were among
hormonal-contraceptive users) and few HIV infections (ten for DMPA and
three for oral contraceptives) occured for these users.
In selecting quotes, the Times article glazed over these and other
possible limitations of the study, including the fact that
contraceptive use was self-reported and not confirmed by the
researchers through examination of clinical records. Contraception
was not provided in all 14 sites used in the study and therefore not
consistent across them. Participants in the study often switched
contraceptive methods: Almost half of the women who reported using
hormonal contraceptives also used non-hormonal methods at some point,
but switching was not taken into account in analyzing the data. All of
these are methodological weaknesses that could skew the results.
The Times also over-stated the conclusiveness of findings on condom
use. Belluck, for example, wrote:
The researchers recorded condom use, essentially excluding the
possibility that increased infection occurred because couples using
contraceptives were less likely to use condoms.
This is not accurate. Condom use in the study was self-reported. It is
very difficult to accurately measure condom use from self-reporting
because people tend to overstate to researchers the consistency with
which they use condoms (a well-known phenomenon), and there was no way
to measure whether couples in the study reporting condom use actually
used condoms during all sex acts, some sex acts and not others, or
even consistently and correctly over the three-month period. The
researchers did control for condom use but based on data that were not
systematically collected to answer these questions. Because of this,
Morrison and Nanda note that the researchers' "analytical adjustment
for condom use might be insufficient." One expert, speaking off the
record, suggested that while the findings of this study absolutely
require further examination, the analysis of condom use alone was
cause for "healthy skepticism" of whether the findings were
conclusive.
---------- Forwarded message ----------
From: Guffran Rostom
Date: Fri, Oct 7, 2011 at 11:02 AM
Subject: Re: [GYCA] NYTimes: Contraceptive Used in Africa May Double
Risk of H.I.V.
To: joya banerjee
Hi Joya!
More insightful than the NYT article:
http://www.rhrealitycheck.org/blog/2011/10/04/hormonal-contraceptives-weighing-evidence-weighing-risks
Best,
G.
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