Blood test may allow for early diagnosis of lymphedema
Levels of a set of proteins circulating in the blood may accurately flag the presence of lymphedema, which currently is difficult to diagnose before the onset of physical symptoms.
At present, the only known way to diagnose lymphedema, an often painful inflammatory condition caused by radiation therapy for cancer, is by means of physical inspection. But by the time the main symptom of swelling of one or more limbs is detectable, the condition may be difficult or impossible to reverse with available treatment options, explained Stanley G. Rockson, MD, senior author of the study describing the new blood test (PLoS ONE, 2012;7:e52021), in a statement from Stanford University Medical Center in Stanford, California. Rockson is a professor of cardiovascular medicine at Stanford University School of Medicine.
Noting that the biological events underlying lymphedema may be present for 5 years or more before physical symptoms indicate the presence of the disease, Rockson's group studied skin-biopsy samples from 63 persons with lymphedema and 27 healthy subjects in an attempt to discover protein analytes that could distinguish diseased tissue from healthy tissue. The researchers focused on genes that were more actively engaged in the generation of their respective protein products in lymphedema vs healthy tissue, eventually narrowing the field to six overproduced proteins through statistical modeling.
Each of the six proteins is associated with at least one of the hallmark features of chronic lymphedema: accumulation of fibrous deposits, stimulation of fat-cell activity, inflammation, and lymphatic-vessel formation. Although none of the six proteins alone was predictive of lymphedema, in aggregate their presence at certain levels and in certain ratios appeared to serve as a biomarker for the condition.
Because levels of these proteins rise early in the course of lymphedema, the biomarker panel could lead to earlier identification of lymphedema risk or onset and earlier treatment that might ease the effects of the condition or even reverse its course.
When Rockson's team evaluated the validity of the biomarker panel using blood samples from an additional cohort of 36 adults with lymphedema and 15 healthy adults, the test was nearly 90% accurate in distinguishing persons with lymphedema from healthy subjects.