Let’s critically analyse data instead of merely reading and quoting abstracts 1 May 2003
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Eleni Papadopulos-Eleopulos,
Biophysicist
Department of Medical Physics, Royal Perth Hospital, Western Australia,
Valendar F Turner, John Papadimitriou, Barry Page, David Causer, Helman Alfonso

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Re: Let’s critically analyse data instead of merely reading and quoting abstracts

Let’s critically analyse data instead of merely reading and quoting abstracts

In his rapid response “Use of CONDOMS for heterosexual intercourse is HIGHLY EFFECTIVE IN PREVENTING HIV TRANSMISSION......” (17th April 2003) Tony misleads again by his use of the word “found” in his statement: “Perhaps the results of de Vincenzi's longitudinal study published in the New England Journal of Medicine (1) mean that she 'found' that: "Consistent use of condoms for heterosexual intercourse is highly effective in preventing the transmission of HIV." If Tony had read not only the abstract of the de Vincenzi study but had also critically analysed her data he certainly would not have suggested that de Vincenzi “found”.

For de Vincenzi (1) to make the above claim, she had first to prove that heterosexual (vaginal) transmission of HIV takes place. She did not.

· In her study, 65% of the index cases were drug users. This means that an unknown number of their partners may have also been drug users. This was acknowledged by Padian in her studies.
· 16.5% of the male index partners were bisexuals. This means that an unknown number of the non-index male partners may have also been bisexual.
· 11 of the 256 couples refused to answer questions about sexual behaviour although the negative partners agreed to follow-up testing. Of the remaining couples, 17.5% were practising anal intercourse at entry into the study and 12.5% during follow-up.

Taking these things into consideration, finding of a positive antibody test in a negative partner during followup cannot be considered as proof for HIV transmission through vaginal intercourse. Although, de Vincenzi did not specify how many of the individuals who seroconverted were practising anal intercourse, she did point out that the seroconversion may have taken place either through “vaginal or anal sex”. She wrote: “Twelve initially uninfected partners seroconverted among the 121 couples using condoms inconsistently for vaginal or anal sex…”.

According to Brody (2): “ ‘The problem of subjects' lying (often euphemistically termed "social desirability responding") about engaging in anal intercourse and intravenous drug use plagues most studies of behavioral risk factors for the transmission of HIV, and the study by de Vincenzi and colleagues is no exception. How was the absence of homosexual contact verified? How was the absence of anal intercourse among the women verified? If only 4 men and 6 women among the 121 couples inconsistently using condoms lied when they denied engaging in anal intercourse (or misreported the facts for other reasons), there would be no cases attributable to vaginal intercourse without a condom. At least this much lying should be expected.”

Regarding the claim that condoms prevent transmission:

· In the de Vincenzi study there was a significant loss (19.5%) to followup.
· The study was conducted in several European countries and HIV testing was performed “in the laboratories of the participating centers”. Since each country uses different criteria for the antibody test, the test was not standardised (www.virusmyth.net/aids/data/vtwbtests.htm).
· The testing was not performed blind.
· Compared to the consistent condom users, Brody pointed out, “The inconsistent condom users in the study by de Vincenzi and colleagues had more than twice the prevalence of anal intercourse at follow-up and also had more sexual contacts.”

According to US researchers (3): “De Vincenzi (Aug. 11 issue)concludes that consistent use of condoms is highly effective in preventing heterosexual transmission of the human immunodeficiency virus (HIV). However, the data analysis is flawed. First, the use of person- years as the unit of comparison for seroconversion rates does not take into account the difference between consistent and inconsistent users of condoms in the frequency of sexual contact. The author reports that the median frequency of sexual contact among the latter was twice that among the former. Once this is accounted for, the seroconversion rate for inconsistent users is 2.5 per 100 person-years (95 percent confidence interval, 1.2 to 5.8), which is not significantly different from the rate of 0 for consistent users (95 percent confidence interval, 0 to 1.5 per 100 person-years).

Second, the author does not adequately define the temporal pattern of seroconversion among inconsistent users of condoms. Those who seroconverted within the first three months of the study were most likely infected before enrollment. Thus, the seroconversion rate for the group of inconsistent condom users may be even lower.”

Again, Tony misleads with his statement regarding heterosexual transmission of HIV: “Whether it is approximately 30%, approximately 90%, or approximately something in between, this would (as supported by de Vincenzi) still be a lot more than precisely zero.”, since such a statement implies that Gisselquist claims a lower limit of approximately 30% which is not the case. Gisselquist (3) wrote “There are many considerations – focused on specific parameters – that suggest that the estimates we present are too high or too low” as we pointed out in our rapid response “Assumptions and opinions do not prove heterosexual transmission of HIV” (15th April 2003). Note, “too high” is not the same as “approximately”.

References

1. de Vincenzi I. A longitudinal study of human immunodeficiency virus transmission by heterosexual partners. European Study Group on Heterosexual Transmission of HIV. N Engl J Med. 1994 Aug 11;331(6):341-6.

2. Brody S. Heterosexual Transmission of HIV. N Engl J Med 1994; 331:1717-1719, Dec 22, 1994.

3. Ambati J., Ambati B. K., Rao A. M. Heterosexual Transmission of HIV. N Engl J Med 1994; 331:1717-1719, Dec 22, 1994.

4. Gisselquist D, Potterat JJ. Heterosexual transmission of HIV in Africa: an empiric estimate. Int J STD AIDS. 2003 Mar;14(3):162-73

Competing interests:   None declared