Subject: Vital Stats: CDC gets AIDS numbers wrong
From: [email-masked]
Date: Mon, 27 Mar 2000 15:49:04 EST

AIDS Ambiguity: See the CDC?
by David Murray
Statistical Assessment Service
<A HREF="http://www.stats.org/">Statistical Assessment Service</A> 

March 27, 2000
 <A HREF="http://www.stats.org/newsletters/0003/cdc.htm">AIDS Ambiguity: See 
the CDC? VitalSTATS March 2000</A> 
 
In previous issues (â-œAIDing and Abetting,â-� July 1999), VitalSTATS has 
castigated some reporters for confusing proportional shifts in declining AIDS 
cases with trends in absolute numbers. In defense of those reporters, it is 
important to note that official statistics from the Centers for Disease 
Control (CDC) have sometimes contributed to the misunderstanding. 

A good example of ambiguity can be found in the January 14 issue of the 
Morbidity and Mortality Weekly Report (MMWR), entitled â-œHIV/AIDS Among 
Racial/Ethnic Minority Men Who Have Sex with Men [MSM] â-` United States, 
1989-1998.â-� The document reads, â-œIn 1989, racial/ethnic minority MSM 
accounted for 24,444 (31%) AIDS cases among MSM, and by 1998, racial/ethnic 
minority MSM accounted for 18,153 (52%) AIDS cases among MSM.â-� 

These data could lead one to believe that the proportional increase in 
minority MSM cases was accompanied by a substantial decline in the absolute 
number of AIDS cases among racial/ethnic MSM between 1989 and 1998. But 
astute MMWR reader (and VitalSTATS fan) Michael Petrelis sensed a 
discrepancy, and took the trouble to check the actual number of cases in 
those respective years. It turns out that the 1989 figure of 24,444 cases was 
for all MSM, including non-minority men, as was the 1998 figure of 18,153 
cases. 

After Petrelis brought the actual data to the attention of the CDC, the 
following â-œclarificationâ-� was appended to the MMWR for February 4, 2000: â-œIn 
1989, racial/ethnic minority MSM accounted for 7,609 (31%) of 24,444 AIDS 
cases among MSM, and by 1998, racial/ethnic minority MSM accounted for 9,429 
(52%) of 18,153 AIDS cases among MSM.â-� 

Hence, since 1989, minority MSM have experienced a 24 percent increase in 
cases. Against the backdrop of a 26 percent decline in total AIDS cases 
during the same time period, the effect was to propel minority MSM cases to 
slightly more than half of all cases by 1998. Perhaps this rise was what Neal 
Nathanson and Judith Aurbach of the Office of AIDS Research at the National 
Institutes of Health had in mind when they wrote in Science magazine (June 
1999) that â-œHIV infection rates continue to climb in a number of population 
groups, such as ... racial and ethnic minorities.â-� 

But the story is even more complicated than that. Even though minority MSM 
increased as a percentage of cases since 1989, there has been a substantial 
drop (from 12,165 to the current 9,429) in the number of such cases since 
1996. In absolute numbers, AIDS is currently declining in every category of 
MSM cases, despite all official appearances to the contrary. 

(Check out the Petrelis web site at www.AIDS-statistics.com)
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Michael Petrelis
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