April 08, 2019
2 min read

Antiphospholipid syndrome affects 1 in 2,000, peak risk among elderly

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Ali Duarte-García

Antiphospholipid syndrome has an estimated prevalence of 50 individuals per 100,000 with an annual incidence rate of 2.1 per 100,000, notably higher among patients older than 55 years, according to data published in Arthritis & Rheumatology.

Antiphospholipid syndrome has been an understudied disease,” Ali Duarte-García, MD, of the Mayo Clinic, told Healio Rheumatology. “It was described more than 30 years ago and, until now, basic knowledge such as its frequency in the population was not known. This information is fundamental to be able to allocate resources for further research and health care delivery.”

According to Duarte-García and colleagues, available studies examining the frequency of APS in the general population have been mostly retrospective in nature, done at major referral medical centers and none were population-based.

To estimate the incidence, prevalence and mortality of antiphospholipid syndrome themselves, Duarte-García and colleagues evaluated data from the Rochester Epidemiology Project, a record linkage system that includes medical records of patients who sought medical care in Olmsted County, Minnesota, which in 2010 had a population of 144,248, 74.7% of whom were aged 18 years or older and 85.7% were white.

Using this database, the researchers identified an inception cohort of patients with antiphospholipid syndrome from 2000-2015. All cases were required to meet the 2006 Sydney criteria, or otherwise have a recorded diagnosis by physician consensus.

In addition, all patients with antiphospholipid syndrome identified from the database and included in the analysis had completed tests for lupus anticoagulant, IgM and IgG aCL and anti-2 glycoprotein-1 antibodies. When calculating the incidence rate, the researchers adjusted for age and sex based on the U.S. white population in 2010. They estimated prevalence based on the incidence rate, assuming stable mortality and that population migration would be independent of disease status.

According to the researchers, there were 33 patients with antiphospholipid syndrome in 2000-2015 that met their inclusion criteria, of whom 55% were women and 97% were white. The annual incidence rate was 2.1 per 100,000 adults (95% CI, 1.4-2.8), with rates similar between men and women.

In addition, the researchers estimated a prevalence of 50 per 100,000 (95% CI, 42-58), with rates also similar among men and women. Among the 33 cases, 18% included a concurrent diagnosis of SLE, and the most frequent clinical manifestation was deep venous thrombosis.

“We found APS frequency is about 1/2000 individuals — or 50/100,000 — with approximately 2-3 new cases every year per 100,000 individuals,” Duarte-García said. “In addition, the disease is more frequent later in life.”


Lastly, the overall mortality of patients with antiphospholipid syndrome did not differ significantly from individuals in the general population, with a standardized mortality ratio of 1.61 (95% CI, 0.74-3.05).

“This population-based study of clinically identified APS is the first to describe basic and fundamental epidemiologic data on incidence, prevalence and mortality rates needed to understand the population burden of APS,” Duarte-García and colleagues wrote.

In an interview with Healio Rheumatology, Duarte-García noted that “epidemiologic data is basic to understand the impact of APS at the population level. The epidemiology of a disease provides basic information to clinicians to do the appropriate testing when approaching symptoms to make a diagnosis. Furthermore, these data can inform policy decisions and resource allocation.”– by Jason Laday

Disclosure: The authors report no relevant financial disclosures.