New Research Finds Pattern For Detecting 'False-positive' ANA Results PDF Print E-mail
Wednesday, 05 January 2011 21:35
taken from http://www.scumdoctor.com/images/Ana-And-Blood-Test.jpgThe presence of antinuclear antibodies (ANA) indicates the possibility of autoimmunity and the indirect immunofluorescence (IIF) assay on HEp-2 cells is the standard blood test (ANA-HEp-2) used to detect ANA. However, studies have shown that a "false-positive" ANA test occurs in up to 13% of healthy individuals. In such cases the test detects the presence of autoantibodies that apparently are not associated with autoimmunity. Researchers from Brazil have now uncovered distinguishing characteristics of the ANA test in healthy individuals and patients with autoimmune disease, reducing the likelihood of an erroneous autoimmune disorder diagnosis. Their findings are published in the January 2011 issue of Arthritis & Rheumatism, a journal of the American College of Rheumatology (ACR).

The immune system is responsible for protecting the body against foreign invaders and infection, but in some individuals the immune system repeatedly attacks healthy cells in the body resulting in an autoimmune disease. According to the Centers for Disease Control and Prevention (CDC) autoimmune diseases—which include rheumatoid arthritis, Sjögren's syndrome, and systemic lupus erythematosus—affect up to 8% (22 million individuals) of the U.S. population.

The Brazilian research team, led by Luis Andrade, MD, PhD, from the Federal University of São Paulo, recruited 918 healthy individuals (634 females and 284 males) between the ages of 18 and 66 years for this study. In the control group were 153 patients with autoimmune rheumatic diseases that included lupus (87), systemic sclerosis (45), Sjögren's syndrome (11) and idiopathic inflammatory myopathy (10). To determine the concentration of ANA in the blood, ANA-HEp-2 tests were run on all participants and considered positive if a well defined IIF pattern was identified.

"The ANA-HEp-2 test is positive in a sizable portion of the general population and our findings established distinguishing characteristics between healthy individuals and patients with autoimmune disease which is essential to accurately interpret the test results," explained Dr. Andrade. Researchers determined that positive ANA-HEp-2 tests in healthy participants occurred predominantly as a nuclear fine speckled (NFS) pattern (at low to moderate titer) or as a nuclear dense fine speckled (NDFS) pattern (frequently at high titer) in 46% and 33% of ANA-positive healthy individuals, respectively. Healthy participants did not present a nuclear coarse speckled (NCS) or a nuclear homogeneous (Ho) pattern.

In those with autoimmune disease the ANA-HEp-2 showed positive results at a predominantly moderate to high titer. A distinct ANA-HEp-2 pattern profile was observed, characterized by the absence of the NDFS pattern and the exclusive occurrence of the NCS (26%), centromeric (8%), nuclear homogeneous (7%), and cytoplasmic dense fine speckled (3%) patterns. ANA-positive patients with confirmed autoimmune diseases also showed the presence of the NFS (42%), but at a higher titer than in healthy individuals.

At the end of a 4-year follow-up period 73% of the ANA-positive healthy individuals retained a positive test result, but did not develop any symptoms of autoimmune rheumatic disease. "Our study confirms that the ANA-HEp-2 pattern is critical in properly diagnosing autoimmune disorders and future research should attempt to reproduce the interpretation of test results among different ANA experts and ANA-HEp-2 slides brands," Dr. Andrade concluded.

Source: The Medical News (2011); Source article can be viewed here.

 
More articles :

» Long-Term Outcomes of Scleroderma Renal Crisis

In a previous study. researchers sought to describe the medical history of a group of patients with Scleroderma Renal Crisis who had been treated with ACE inhibitors. The following is essentially a summary of that study, which was conducted by...

» Skin Autofluorescence Is Not Increased in Patients with Systemic Sclerosis

M. E. Hettema, H. Bootsma, R. Graaff, R. de Vries, C. G. M. Kallenberg, and A. J. SmitReceived 24 May 2011; Accepted 8 August 2011Vascular involvement is a key factor in major manifestations of systemic sclerosis (SSc), such as Raynaud’s...

» Systemic Sclerosis: A Bird’s Eye Review of Recent Literature

Pathogenesis and new therapeutical targetsTranscription factor Fos-related antigen-2 induces progressive peripheral vasculopathy in mice closely resembling human systemic sclerosis: In this study the authors investigated the potential pathogenetic...

» Genetics of Scleroderma: Implications For Personalized Medicine

Significant advances have been made in understanding the genetic basis of systemic sclerosis (scleroderma) in recent years. Can these discoveries lead to individualized monitoring and treatment? Besides robustly replicated genetic susceptibility...

» Caution Needed When Using ACE Inhibitors in Scleroderma

Exposure to angiotensin-converting enzyme inhibitors prior to the onset of renal crisis in patients with increases the risk of death, according to 1-year findings from the prospective observational International Scleroderma Renal Crisis Survey.The...

» A Simple Blood Test Could Hold The Clue...

In a recent press release, the reported that a simple blood test could hold the clue and may even save lives. is a common condition, especially in teenagers, affecting approximately 10 million people in the UK. It can vary from being mild to very...