New diagnostic code for ultrarare primary immunodeficiency promises multiple benefits

Renee Hilgren’s son was first diagnosed with primary immunodeficiency (PI) in 1992 when he was three years old. Back then, his symptoms didn’t fit neatly with any of the known PI diagnoses. In fact, his specific condition hadn’t been discovered yet. It wouldn’t appear in the medical literature until 2013 when researchers at the National Institutes of Health described an ultrarare PI called PASLI disease or activated PI3K delta syndrome (APDS).

Now, less than a decade after APDS’ discovery, it’s getting its very own diagnostic code. Called an ICD-10 code, which stands for the International Statistical Classification of Diseases and Related Health Problems, 10th Edition, it’s a milestone that may not sound exciting but heralds important recognition for the disorder.

From health agencies to doctor’s offices to insurance companies, ICD-10 codes are a critical part of the medical system’s infrastructure. They allow different entities to communicate patients’ conditions accurately and consistently. As a result, they underpin everything from medical billing to public health statistics. In fact, these codes are so important that the EveryLife Foundation for Rare Diseases developed a toolkit to help rare disease advocates navigate the process of getting an ICD-10 code for their condition. As Immune Deficiency Foundation vice president of advocacy Lynn Albizo put it, having a specific code is like “ok, we have a name for this.”

The APDS ICD-10 code, D81.82, goes into effect on October 1, 2022. Over time, the new code will allow for dedicated tracking of APDS patients, systematic data collection on treatments and outcomes, and easier communication between doctors’ offices and insurance providers. The code may also raise awareness of APDS among healthcare providers who have patients like Hilgren’s son—with a primary immunodeficiency that doesn’t quite seem to fit other diagnoses.

Currently, APDS is considered an extremely rare PI, with an estimated prevalence of 1 in 1-2 million people. But because patients lack standardized notation of an APDS diagnosis in their electronic medical records, it’s hard to know for sure. “It seems rare now, but maybe there’s a lot more [APDS patients] out there than we think,” Hilgren commented. 

Hilgren noted that genetic testing for APDS, which wasn’t available in 1992, ultimately led to her son’s definitive diagnosis in March 2021. He was 32 and suffering from aggressive lymphoma. Doctors began looking into his undefined PI when his cancer failed to respond to chemotherapy. He was ultimately treated with an allogeneic stem cell transplant and has been doing well since then.

In fact, APDS can easily be confused with other PIs like common variable immunodeficiency (CVID). It is a combined immunodeficiency, with symptoms that include frequent respiratory tract infections, chronic infection with certain viruses (for example, Epstein-Barr virus, cytomegalovirus, or herpes simplex virus), increased generation of white blood cells, an enlarged spleen or liver, and inflammation of the small intestines. But, these symptoms can vary widely from person to person. 

Making and tracking diagnoses is not the only challenge with an ultrarare disease. APDS also lacks clinical care guidelines. Although case reports and medical reviews paint a picture of how patients have been cared for by individual clinicians, an ICD-10 code will allow the analysis of treatment and procedure codes from patient medical records. With this larger and more comprehensive picture, experts can evaluate and standardize care for the condition. 

And insurers can in turn ensure that claims with the APDS ICD-10 code that match care guidelines are covered without extra, burdensome paperwork. Said Albizo, “In general, [a specific ICD-10 code] can remove barriers to coverage.”

Referring to her son’s longtime immunologist, who is now retired, Hilgren said “He always said that he could never put our son in a box. There was always something just a little different than the other PIs that were out there. If he only knew the journey and the genetic confirmation…I believe he’d be just over the moon with this, that his hunch was right.”

Learn more about activated PI3K-delta syndrome (APDS) in an upcoming IDF Lunch & Learn on August 24, 2022.

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