With all of the marvelous visibility given to ALS, I hope that our organizations will embrace all questions and be part of a very public and continuing conversation about ALS.
One part of the article jumped out at me --
But ALS is also, by any definition, a rare disease; the threshold specified in the federal Rare Disease Act of 2002 is a nationwide incidence of 200,000 patients. The CDC estimates the prevalence of ALS in the U.S. at about 12,000 persons. The ALS Association says 30,000, but hasn't responded to my inquiry about the discrepancy.I hope that the ALS Association has responded by now, and if they have, we would all benefit from their insights. If they've not, I'll take a stab at it. Forgive me if I sound like a middle-school math teacher, but it's my comfort zone.
Yes, legally, rare diseases are those "affecting fewer than 200,000 people in the U.S." "Affecting" is usually interpreted as "having it at any given moment." That's prevalence.
Let's consider a factory. The assembly line produces things and the warehouse holds things. Prevalence is like the warehouse. Incidence (the number of people diagnosed with a disease in a time period) describes the speed of the assembly line.
ALS is a high-incidence (you're very likely to get ALS -- as likely to get ALS as MS), low-prevalence (you're not likely to be alive with ALS) disease. ALS has a fast assembly line and a very small warehouse. What happens to everyone who doesn't fit in that small prevalence warehouse? It's not good.
Now for the discrepancy. All ALS numbers in the United States are extrapolated, based on smaller studies. We don't have mandatory reporting of ALS by physicians. Nobody is really counting every nose. And you can sense that with the fast-moving numbers in and out of that prevalence warehouse that the numbers don't stand still very long.
The 30,000 number is a swag. It has been used by organizations for decades. In perhaps the only area where ALS organizations have cooperated and shared data, they have been complicit in propagating a 30,000 number that has been convenient but not well-rooted in reality. ALSA has actually been quietly distancing itself from the 30,000. Why? As I said, nobody is counting noses and some people have a fixation on prevalence as being the important number. It's not. It's a one-legged data stool. If you talk about a small warehouse without paying any attention to the speed of the assembly line, you miss the boat on the impact of a disease (or as I sometimes call ALS, a "diesease").
We're pretty sure that around 5500-6000 Americans are diagnosed with ALS every year. Arithmetic tells us that if they live an average of 3 years after diagnosis, then we're talking around 16,000-18,000 Americans alive with ALS at any moment. If they live an average of 5 years post dx, then maybe the number could approach 30,000, but that's a stretch.
Now for that 12,000 number that was published in the recent CDC ATSDR ALS Registry report. This gets interesting. We have paid over $40 million taxpayer dollars for a national registry and this was the first published report. They gathered data from Medicare (people with ALS usually go on to Medicare quickly), Medicaid, and VA files along with a self-enrollment web portal. They identified just over 12,000 people alive with ALS in the U.S. in a one-year period. Ugh. How many Americans were living with ALS in that period who were not in those government files and who did not self-enroll? We simply don't know. How complete was their counting technique? We just don't know.
And the clunker in all this is that the Registry did not address incidence (that pesky assembly line speed) at all in that period. It gave us a one-legged data stool of a very low prevalence with no other supporting incidence or mortality data.
ALSA is obviously proud of getting the ALS Registry project passed. I so hope that they have answered Mr. Hiltzik's question by now. If not, you have my answer.
And with ALS in a wonderful national spotlight right now, what better time is there to talk of the correct numbers correctly? ALS is a high-incidence, low-prevalence disease, and that's a troubling combination that should make every American squirm.
#ALSicebucketchallenge #icebucketchallenge #strikeoutals