Diagnosing Sarcoidosis with Lung Fluid Sample Ratio Has Potential as Complementary Tool

Analyzing the bronchoalveolar lavage fluid (called BALF, it is a small sample of the fluid present in the lungs) for the ratio of immune CD4 and CD8 cells may improve the diagnosis of sarcoidosis, according to the results of a recent study.

BALF is collected through a medical procedure using a bronchoscope that is passed through the mouth or nose into the lungs.

The study, “Diagnostic Performance of Bronchoalveolar Lavage Fluid CD4/CD8 Ratio for Sarcoidosis: A Meta-analysis,” was published in the journal EBioMedicine.

Clinicians who diagnose sarcoidosis, a chronic inflammatory disease, often still rely on invasive methods such as biopsies. As a result, researchers are looking for reliable, less-invasive methods for the diagnosis of the disease.

Growing evidence suggests that analyzing the content of BALF is a potential novel method for diagnosing sarcoidosis. Patients with sarcoidosis have shown altered levels of immune system cells and markers in BALF, particularly increased levels of lymphocytosis (an increase in the number of lymphocytes — white blood cells — in the blood) and the ratio of CD4/CD8 cells. The CD4/CD8 ratio is a standard lab test that looks into the ratio of two important types of white blood cells in our blood and is a reflection of the health of the immune system.

While several studies have suggested that the BALF CD4/CD8 ratio is a better tool for diagnosing sarcoidosis compared to other methods, it’s still a controversial view, in part because the BALF CD4/CD8 ratio has been linked to variable sensitivity and specificity.

Researchers investigated the diagnostic usefulness of BALF CD4/CD8 ratio through a meta-analysis to estimate the overall diagnostic accuracy of the ratio. The team looked for studies in different databases (including PubMed, OVID, Web of Science, Scopus, and others), assessing the following parameters: sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR).

In total, 16 studies were considered in the analysis, with 1,885 subjects. After analyzing all studies, researchers found the following values for BALF CD4/CD8 ratio: sensitivity 0.70; specificity, 0.83; PLR 4.04; and NLR 0.36. The diagnostic odds ratio registered 11.17.

These values indicate that BALF CD4/CD8 ratio has a relatively low diagnostic sensitivity and a relatively low ability to discriminate sarcoidosis from non-sarcoidosis, based on the PLR and NLR levels.

These results mean that while BALF CD4/CD8 ratio alone is not robust and reliable enough as a diagnostic tool for sarcoidosis, it may improve a diagnosis of sarcoidosis when taken together with other diagnostic factors.