Blood test demonstrates high accuracy in identifying sarcoidosis

Key takeaways:

• A blood test was able to tell sarcoidosis apart from tuberculosis and lung cancer.
• Researchers said this method will need to be tested further before it can be used in clinics.

A blood test was capable of distinguishing sarcoidosis from other respiratory diseases using disease-specific antigen biomarkers/epitopes, according to results published in American Journal of Respiratory and Critical Care Medicine.

Lobelia Samavati

“This result will impact lots of other autoimmune diseases,” Lobelia Samavati, MD, professor of medicine and molecular medicine and genetics at Wayne State University, told Healio. “The discovery of specific antigens will open new field for diagnosis and treatment of this disease.”

Before designing the blood test, researchers had to obtain genetic material from lung fluid samples and blood cells of patients with sarcoidosis to discover antigens related to the condition. According to an NIH press release, this process, along with molecular techniques, allowed the researchers to find two disease-specific antigen biomarkers/epitopes that bind solely to antibodies of patients with sarcoidosis: Cofilinμ and Chain A.

With this knowledge, Samavati and colleagues developed a blood test and analyzed blood samples from 186 patients with sarcoidosis, 70 patients with tuberculosis, 30 patients with lung cancer and 100 individuals deemed healthy to validate the test and see how well it can distinguish sarcoidosis from other respiratory conditions.

Researchers performed five-fold cross-validation adjusted for confounders to assess the sensitivity, specificity and accuracy of Cofilinμ immunoglobin G (IgG) and Chain A IgG for detecting sarcoidosis.

The Chain A model demonstrated high mean sensitivity (0.9), specificity (0.835), accuracy (0.866) positive predictive value (0.841) and negative predictive value (0.902). Researchers observed comparable high values in the Cofilinμ model, with a mean sensitivity of 0.956, specificity of 0.897, accuracy of 0.925, positive predictive value of 0.896 and negative predictive value of 0.956.

After including Chain A and Cofilinμ IgG together in one model, researchers noted improved mean sensitivity (0.977), specificity (0.882), accuracy (0.928), positive predictive value (0.886) and negative predictive value (0.978) for identifying sarcoidosis among other respiratory conditions.

Notably, both Cofilinμ and Chain A IgG are significantly correlated to the current sarcoidosis markers of lysozyme, angiotensin-converting enzyme, soluble interleukin-2 receptor and C-reactive protein, according to researchers.

Samavati said in an NIH press release that this method will need to be tested further before it can be used in clinics.

“[In future studies,] we would like to further expand our observation and assay other diseases,” Samavati told Healio.

“We would like to bring the test to FDA as a specific diagnostic test, for which we require to acquire venture capital,” she added.

Reference:

• Scientists develop a simple blood test to quickly diagnose sarcoidosis. https://www.nih.gov/news-events/news-releases/scientists-develop-simple-blood-test-quickly-diagnose-sarcoidosis. Published Feb. 22, 2024. Accessed Feb. 22, 2024.