The risk of blood clots nearly doubles in people with cold agglutinin disease (CAD) compared with that seen in patients with other conditions, a large data study from the U.S. reports.
In this disease, autoantibodies called cold agglutinins target blood cells to be destroyed by the immune system. Hemolysis, or rupture of red blood cells, can occur both inside and outside blood vessels.
Thrombotic events (TEs), which refer to clots that obstruct blood flow, are known to be more prevalent in patients with several types of hemolysis. Such complications not only affect quality of life, but also increase disease burden and cost of treatment. Still, few studies have explored the incidence of TEs in people with cold agglutinin disease.
Researchers at the MedStar Georgetown University Hospital, with colleagues at EpidStrategies and Bioverativ (a Sanofi company), evaluated the risk of clots in a large group of CAD patients registered with the Optum Claims-Clinical database. The data set provides electronic medical records and adjudicated claims covering about 55 million patients in the U.S.
In total, they collected data on 608 adults with CAD (age 25 and older), and 5,873 patients without cold agglutinin disease serving as a control group. All were matched for sex, age, race, region of residence, and time (and year of entry) in the Optum health plan. Participants were enrolled from 2006 to 2016.
Most (around 70%) of these people were 65 or older, 63% were women, and 85% were white. Nearly 46% lived in the Midwest and 26% resided in the South.
On average, cold agglutinin disease patients were followed in the Optum system for a mean of 7.5 years, and controls for about 8.1 years.
During this time, 180 CAD patients had at least one TE, corresponding to a 29.6% incidence rate, an analysis found. This rate was lower, 17.6%, in people without this disease.
Thrombotic events in veins occurred in 14.6% of CAD patients and 5.2% in controls, while arterial TEs occurred in 7.6% of the CAD group and 3.7% of controls. Clots in the brain were observed in 14% of CAD patients and 11.6% of patients without CAD.
Overall, the incidence rate of TEs was 14.2 per 100 person-years in CAD patients, and 6.0 for non-CAD participants. (Person-years is a measure that sums actual follow-up time for each patient, and is higher with more years in study.)
The overall risk of a TE was 1.94 times higher for those with cold agglutinin disease, than for those without it, throughout the follow-up period.
The prevalence of TEs was also higher in patients with presumed primary CAD (not due to other causes) than in matched controls, 26.8% vs. 16.5%.
When the researchers divided participants according to their Charlson Comorbidity Index (CCI), a measure of additional complications, they observed a consistently higher risk of thrombotic events in CAD patients than in controls. This risk was highest among CAD patients without comorbidities.
In a subsequent analysis considering use of anticoagulants, an inferior vena cava (IVC) filter, and mortality, the risk was 3.1 times in CAD patients than in controls. (An IVC filter is placed in the inferior vena cava, a large vein in the abdomen that returns blood from the lower half of the body to the heart, to prevent blood clots from reaching the heart and lungs.)
Researchers also found that hospitalized CAD patients with no registered clots in the six months before admission had a TE incident rate of 10%, almost double the rate in hospitalized non-CAD patients (5.4%) — representing a 1.87 times higher risk in the CAD group.
Overall, these findings suggest that cold agglutinin disease patients have a significantly greater TEs rate than do similar patient groups with other conditions.
“This study demonstrates for the first time that CAD is associated with a significantly increased risk of TEs,” the researchers wrote.
“The morbidity and potential mortality associated with TEs in patients with CAD should not be underestimated,” they added.
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