Re: "HIV" and PCP 18 October 2004
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Peter J Flegg,
Physician
Blackpool, UK, FY3 8NR

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Re: Re: "HIV" and PCP

Among the many failings of the Perth Group, their inability to understand the field of HIV medicine is exceeded only by their penchant to misrepresent other peoples’ data. Whilst I can personally sympathise with their ignorance about the details of retrovirology, I must deplore their constant efforts to twist the research findings of real scientists to try and support their own lost cause.

In an attempt to deny the link between Pneumocystis and HIV/AIDS, they serve up a paper published in 1991 as evidence that PCP has nothing to do with AIDS [1]. I have stated that PCP is extremely unusual in the absence of HIV, a fact they dispute. They ask me,"Can the diagnosis of PCP in five immunocompetent, "HIV" negative individuals in one hospital, within 3 months, be considered as evidence that PCP is "extremely unusual" in the absence of HIV?".

The answer is "Yes, it can", and not just because I say so, but because the article’s authors say so themselves. They published the case series precisely because PCP is "extremely unusual" in the absence of HIV. Here are some further direct quotes, so there can be doubt:

"Before 1981 [when PCP was first described in AIDS patients] it was a rare condition. Pnemocystis carinii pneumonia was first reported in the United States in 1955, and only 107 cases were reported during the subsequent decade" [interpretative hint to Perth Group - this means "rare"]

"Reports of PCP in non-immunocompromised adults are extremely rare." [Interpretative hint to Perth Group – this means "extremely rare"]

The paper in question actually does not give details of five cases of PCP in "immunocompetent" individuals as the Perth Group would have us believe. The cases were billed as: "A Cluster of Pneumocystis Carinii Pneumonia in Adults without predisposing illnesses" in the article's title, and in the text were billed as "a cluster in five elderly patients without AIDS or other identifiable risk factors" [by which the authors mean recognised risk factors for PCP such as lymphoproliferative disease etc.]

Of the five cases, all in people over 65, there was one woman with diabetes, CCF and asthma, one man with diabetes and alcohol abuse, one woman with cardiac valve disease, one woman with COPD and CCF, and the only case below the age of 70 was in a healthy male. Immunological studies on three of the five cases showed normal CD4 count in only one, and all three had low CD8 counts and evidence of a "cellular immunodeficiency as demonstrated by the low stimulation indexes in response to mitogen and antigen".

So it would seem that perhaps they were not as immunocompetent as the Perth Group would have us believe, and certainly not as immunocompetent as we would expect 30 year olds to be (who have the highest incidence of HIV-PCP). This is all rather irrelevant, however, because even if they were fully immunocompetent, this in no way detracts from the recognition that PCP in the absence of HIV immunodeficiency is exceedingly rare, a point the Perth group seem to keep trying to disclaim, even though their own citations merely confirm it.

Let us put these 5 cases into perspective. In 1991, the year this series was published, there were over 20 thousand reported cases of PCP in AIDS patients in the USA alone [2]. This huge disparity in cases is precisely why non-HIV cases of PCP continue get written up in journals – it is because they are the exception, and not the rule.

[1] Jacobs JL, Libby DM, Winters RA, Gelmont DM, Fried ED, Hartman BJ, et al. A Cluster of Pneumocystis Carinii Pneumonia in Adults without predisposing illnesses. N Engl J Med 1991;324:246-250.

[2] http://www.cdc.gov/hiv/stats/surveillance91.pdf (page 15)

Competing interests: None declared