Wednesday, March 21, 2018

Perception bias in T1D communities: late onset type 1 diabetes

T1D communities are often very vocal when it comes to the issue of initial Type 1 Diabetes. This is especially true when a case of late diagnosis leading to a fatal or debilitating DKA goes viral. At that point, prayers and thoughts (which are as effective in preventing diabetes or treating DKA as they are in school shootings and gun control) fly and the T1D community erupts in “know the signs” memes and aggressive comments about medical professional who, at best, are accused of not doing what they should be doing, namely finger pricking every case of stomach flu they encounter. That measure that would be expensive, hard to interpret, lead to a lot of even more expensive confirmation tests. While they would probably yield a few earlier diagnosis, even fewer early stage DKA detections, the benefits – in the current state of therapies – would be nil in terms of long term prognosis and minimal in terms of DKA complications (ease of access to quality health care matters much more in terms of initial DKA prognosis, initial DKA isn’t a major factor in morbidity/mortality).

One of the latest circulating memes, recycling the “know the signs” memes, is that you can catch T1D at any age (true, although the onset is definitely skewed towards the young) and that T1D is often misdiagnosed as T2D. That’s understandable given the fact that T1D communities will have their fair share of members who have been diagnosed T1D after a misdiagnosis of T2D.

However, the T1D communities perception of “misdiagnosed” T1D is the result of multiple biases.

- Adult T2Ds far outnumber T1Ds.
- T2Ds who were initially misdiagnosed as T1Ds are unlikely to hang around in T1D communities.
- T1Ds who were initially misdiagnosed as T2Ds are likely to join T1D communities and likely to be unhappy and vocal about their misdiagnosis.

What’s the reality?

In fact, the issue is well known and well recognized

Late-onset type 1 diabetes is difficult to diagnose in people aged 31–60 years because it represents only a small minority of patients diagnosed with diabetes; its misdiagnosis as type 2 diabetes results in inappropriate treatment. (quote from the paper below)

However, given the huge discrepancy in the size of the respective populations, what actually happens in terms of diagnosis mistakes is the exact opposite of what the T1D communities are worried about.

Errors are often made when diagnosing type 1 diabetes later in life. For example, more than 50% of patients diagnosed with type 1 diabetes after age 35 years were shown to have type 2 diabetes in long-term follow-up. (quote from the paper below)

That issue is, for example, addressed in “Frequency and phenotype of type 1 diabetes in the first six decades of life: a cross-sectional, genetically stratified survival analysis from UK Biobank” (free full text).

One of the sensible ways to improve diagnosis accuracy as far as adult onset T1D and T2D is to take genetic predisposition factors into account.

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