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Misdiagnosis of Latent Autoimmune Diabetes in Adults

Nov 17, 2018
 
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Arsalan Hashmi, PharmD. Candidate, LECOM College of Pharmacy

Although there are no guidelines for LADA, prescribers should take a closer look at their patients before diagnosing T2D.

The misdiagnosis of latent autoimmune diabetes in adults, or LADA, is unfortunately very common. Patients who present with hyperglycemia and are over the age of 30 many times get labeled as having type 2 simply because of their age. LADA is known as type 1.5 diabetes, and according to Marie Nierras from the Juvenile Diabetes Research Foundation the biggest difference between T1D and LADA is that adults have a slower progression of the autoimmune disease. This slow destruction in beta cells is initially why it is so difficult to distinguish between type 1 vs type 2 diabetes in adults.

Nicholas Thomas, who presented the study at the 2018 EASD pointed out that because of the very low prevalence of type one diabetes in adults along with rising obesity rates in the general population, it is nearly impossible to distinguish the two. This study looked to identify similarities in patients who have LADA and further examine their clinical experiences.

This was a 10-year study that looked at almost 600 adults with T2D diagnosed past the age of 30 being treated with insulin and found a large number had been misdiagnosed and initially treated for type 2 diabetes. T1D was defined as needing recurring insulin injections within three years and a C peptide level of less than 200 pmol/L. The 3-year period was given to account for the honeymoon period in type 1 diabetes. There was 21% (123 participants) who fell into this group. The “placebo” group consisted of 220 people with type 1 who were diagnosed under the age of 30.

Within one year following diagnosis, 84% of the 123 participants needed insulin. This finding did not line up with the current understanding that LADA has a slow progression. People over 30 years old who have type 1 had the same characteristics and risk scores as their counterparts under 30 who have type 1, however their treatments were very different. Nearly all people under 30 who have type 1 received initial insulin, compared to only 62% in the over-30 group.

There were, however, significant differences between T1D and T2D both diagnosed after the age of 30 as seen in the chart below.

T1D T2D
Ave BMI 25.9 31.6
Positive Islet Autoantibody 78% 6%
T1D Genetic Risk Score 0.268 0.229

The above tests are helpful in suspected LADA, but there is no perfect test for determining T1 from T2 diabetes since the islet antibody and genetic risk score may not always be accurate. For example, both doctors said it’s possible that autoantibodies test positive in type 2 and negative in a type 1. Thomas says doctors should reconsider the diagnoses of any person who has type 1 who proceeds to insulin shortly after diagnosis and that the sooner these misdiagnosed patients start receiving insulin, the less likely they’ll have complications like diabetic ketoacidosis. However, Dr. Colin Dayan, who conducted the study, feels that if type 1 diabetes is suspected in a patient, they should first be given oral medication and closely watched for signs of further decline before initiating insulin therapy.

He states that there are ketones tests and other ways to prevent DKA in patients, and that the change in diagnosis and treatment should be a careful one. Currently, there are no guidelines from the CDC relating to diagnosing LADA, so prescribers are left to their own judgment to distinguish type 1 diabetes from type 2. Dr. Thomas and team are working on diagnostic algorithms to guide prescribers in this new field.

Practice Pearls:

  • This study shows that there is a difference in BMI, islet autoantibody presence, and T1D genetic testing that providers can use if they suspect latent autoimmune diabetes in adults (LADA).
  • Currently there are no diagnostic guidelines for distinguishing LADA and providers should use their best clinical judgement on when to switch to insulin.
  • Any patient requiring insulin within a year after type 2 diagnosis should be assessed for LADA.

References:

Misdiagnosis of Adult-Onset Type 1 Diabetes Is Common – Medscape – Oct 18, 2018.

Price, Cathrine. “Clarifying LADA (Type 1 Diabetes in Adults).” Healthline, Healthline Media, 2018, www.healthline.com/diabetesmine/clarifying-lada-type-1-diabetes-in-adults#1.

Arsalan Hashmi, Pharm. D. Candidate 2019, LECOM School of Pharmacy