GOOD (HIDDEN) NEWS ABOUT THE AIDS EPIDEMIC
By Robert Root-Bernstein
The Wall Street Journal 2 Dec. 1993
Statistics of any kind are difficult to interpret, and AIDS statistics
are no exception. Indeed, the latest statistics released by the Centers
for Disease Control are so odd as to be virtually indecipherable. One begins
to suspect the difficulties have been introduced on purpose.
On Oct. 30, the CDC released a report contending that AIDS has become
the top killer of U.S. males age 25 to 44, and the fourth leading killer
of women in the same age group-statistics that received wide currency in
the lead-up to World AIDS Day yesterday. Although the report states clearly
that part of the reason for the sudden upsurge in AIDS cases is due to
a new expanded definition that went into effect a year ago, it nonetheless
presents the data so that the implications of this change are far from
obvious. Between January and September of 1992, 60,656 people were diagnosed
with AIDS and reported to the CDC. Between January and September of this
year, 85,526 new AIDS patients were reported to the CDC, an increase of
41% from the year-earlier period. One's first impression is that the epidemic
continues to worsen.
The CDC report immediately cautions that the huge increase in new AIDS
cases does not mean that AIDS is mushrooming. Most of the increase, it
says, is due to changes in the definition of AIDS that vastly expanded
the diagnostic criteria at the beginning of this year. These definitional
changes were predicted to more than double the number of reported cases
and, indeed, the number of cases reported under the new definition account
for more than half of all those reported so far this year.
Interestingly, though, no one seems to have noticed that if the number
of cases diagnosed under the new definition was to be more than twice the
number found under the old definition, and AIDS has continued to grow at
the same rate as before, then the total number of AIDS cases reported this
year should be not 41% higher than for the same period last year but more
than 100% higher. Why the discrepancy? Even odder, CDC officials claim
that when the new definitional bias is taken into account, AIDS is only
increasing about 3% to 5% a year, as it has been since 1990.
The definitional changes simply allowed many people who were going to
get AIDS someday (according to the old definition) to be diagnosed (and
treated) sooner. That is good for peoplewith AIDS, but what does it do
to our ability to track the course of the epidemic?
The CDC itself admits that over half of the new cases reported this
year are due to the new definition: 48,915 of the 85,526. In other words,
only 36,611 of the AIDS cases reported so far this year would have qualified
as AIDS cases according to the old definition. That is 20,045 fewer AIDS
patients in 1993 than the 60,656 diagnosed during the same nine months
in 1992. This is a drop of 33%, not an increase of 3% to 5%.
So, are AIDS cases increasing steadily at 3% to 5% a year, as the CDC
claims without any apparent justification - or are they decreasing drastically
by some 30%? If all the people who have been diagnosed as having AIDS according
to the new definition would eventually have been diagnosed as having AIDS
according to the old definition a fact the CDC itself admits- then is it
not possible to see the current glut of large numbers as a form of artificial
inflation designed to impress the CDC's clients just at a time when, in
fact, the AIDS epidemic may have peaked and be on its way down?
The crucial information is the number of people who would have been
diagnosed with AIDS according to the new definition had it been in place
in 1992, or 1990, or even 1985. These data do not, and can never, exist.
Even worse, this is not the first time that the definition of AIDS has
been altered to increase the number of diagnoses. The definition change
implemented in 1985 increased the number of AIDS diagnoses about 2% a year
over the 1984 definition; the 1987 change increased new diagnoses 30% to
40% a year; and now the new changes more than double the number. Anyone
simply plotting AIDS statistics provided by the CDC year by year will be
terribly misled by the resulting graph for the simple reason that the numbers
represent apples one year; apples and oranges another; apples, oranges
and bananas a few years later; and so forth.
As James O. Mason, assistant secretary of health and human services,
told the Los Angeles Times in 1991 when the latest alterations were proposed,
changing definitions "messes up the baseline for comparison from past
to future" and "will make the interpretation of trends in incidence
and characteristics of cases more difficult." Perhaps that is the
Perhaps the CDC does not want anyone to recognize what some statisticians
and actuaries have been predicting for several years now; that AIDS peaked
sometime between 1989 and 1992 in the U.S. and is on its way down. Indeed,
according to one of the best validated principles of epidemiology - Farr's
law - the epidemic should proceed at the same rate that it arose.
Think of it: Perhaps those people who were most susceptible to AIDS
have already contracted the disease and it will remain within high risk
groups, as the National Research council report predicted last year. Or
even better, maybe safer sex campaigns, clean needle exchanges and better
health care are having their effects. Is it really so unthinkable that
there is good news on the AIDS front that we cannot face it when it appears?
The upshot of this lesson is a simple one. The CDC is comparing apples
with apples and oranges. That it can get away with such sleights of hand
only goes to show how really deeply innumeracy runs in this society; innumeracy
so pervasive that not even our science reporters, our AIDS activists and
our researchers seem to notice. Or is it worse, even, than not noticing.
Have we reached the stage in AIDS advocacy that we will mislead in order
to succeed? *