ANA prevalence in US increased from 11% to 16% over 25 years
Click Here to Manage Email Alerts
Antinuclear antibody prevalence in the United States has grown from 11% during the period of 1988 to 1991, to 16.1% during 2011 to 2012, according to data published in Arthritis & Rheumatology.
However, the researchers cautioned that studies examining prevalence in varying sociodemographic groups are needed to further understand the increases in specific groups.
“Recent studies have suggested increases in autoimmunity and autoimmune diseases around the world, but the findings are limited by the lack of systematic data, evolving approaches and definitions, and possible physician and referral biases,” Frederick W. Miller, MD, PhD, of the NIH National Institute of Environmental Health Sciences, in Durham, North Carolina, told Healio.
“The CDC National Health and Nutrition Examination Survey (NHANES) databases and repositories offered unique population-representative resources to sample the entire United States, and definitively assess any changes in the frequency of antinuclear antibodies (ANA), the most commonly tested biomarkers of autoimmunity,” he added.
To measure how the prevalence of ANA in the United States has changed over the past 25 years, Miller and colleagues analyzed data from the NHANES, a nationally representative source of noninstitutionalized patients within the country. All participants within the survey cohort completed questionnaires, with many also providing blood samples. The surveys included data such as demographic information, health variables, height, weight and BMI. When considering the data, the researchers factored in sex, age and race as potential explanatory variables.
Serum samples were evaluated for ANA by indirect immunofluorescence. Images of the samples were captured with an automated microscope system and were consequently stored digitally. Images were analyzed and graded on a scale of zero to four, with scores of one to four indicating ANA positivity. Two blinded investigators assessed the samples, and repeat testing resulted in higher than 98% agreement.
The analysis included 13,519 patients aged 12 years or older, with roughly one-third of the cohort coming from each of the assessed time periods — 1988 to 1991, 1999 to 2004 and 2011 to 2012. The prevalence of ANA was 11% in 1988 to 1991 (95% CI, 9.7%-12.6%), 11.4% in 1999 to 2004 (95% CI, 10.02%-12.8%), and 16.1% in 2011 to 2012 (95% CI, 14.4%-18%).
ANA prevalence increased in both sexes, adults aged 50 years or older and non-Hispanic whites, according to the researchers. The changes did not correlate with weight, smoking or alcohol consumption.
“This study provides the first conclusive evidence of increasing autoimmunity in the United States, rising from 22 million in 1988 to 1991 to more than 41 million affected individuals in 2011 to 2012,” Miller said. “Of interest and concern, teenagers and those more than 50 years old had the largest increases in ANA over these 2 decades.
“Although not all persons with ANA develop autoimmune diseases, these autoantibodies are among the first markers of immune system dysregulation that can later lead to autoimmune disease,” he added. “The causes for these increases are not known, but likely candidates are the many changes in our environment relating to our diets, to lifestyle and stress factors, to infections, to chemical exposures and to the many impacts of climate change.”
Perspective
Back to Top
David A. McLain, MD, MACR, FACP, FRCP
In 2010, the American College of Rheumatology published a study affirming that indirect immunofluorescence (IIF) staining with HEp-2 cells should be considered the gold standard for detecting ANAs. However, due to variability in technique, HEp-2 preparation and antibody expression, HEp-2 IIF results have been difficult to standardize. Systemic autoimmune disorders affect 3% to 5% of the general population, and antinuclear antibodies (ANAs) are one of the few specific disease markers in their diagnosis.
Therefore, ANA testing is often the first step in diagnosing systemic autoimmune connective tissue disease (CTD). The presence of ANA has been considered the hallmark or “gold standard” for diagnosing CTD. ANA positivity is, for all practical purposes, required to make a diagnosis of lupus since more than 99% of patients with systemic lupus erythematosus have significant levels of this autoantibody detected at some time during the course of disease. One recent analysis found 7% of SLE patients were ANA negative and a study by Pisetsky, et al found 12% were ANA negative.
However, since the prevalence of SLE is low, most individuals presenting to a physician with ANA positivity do not in fact have lupus and are not at high risk for developing this disease. Unlike cardiovascular disease, there are few available quantitative and objective measures to establish a prognosis for an individual with a positive ANA.
We all know the caveats associated with ANA. Diagnosis cannot be made on the basis of ANA detection alone. The physician must interpret these results in conjunction with the patient’s history and symptoms, physical findings, and other diagnostic procedures. Treatment should not be initiated on the sole basis of a positive test for ANA. Clinical indications, other laboratory findings, and the physician’s — usually a rheumatologist — clinical impression must be considered before any treatment is initiated.
Positive ANA will undoubtedly continue to be a source of consults for rheumatologists, and per this article, the frequency in the general population is increasing.
Collapse
Read more about
Click Here to Manage Email Alerts