NEW YORK (Reuters Health) – About 14% of cases of deep vein thrombosis occur in the upper extremities, according to Canadian and US researchers.

Dr. Frederick A. Spencer of McMaster University, Hamilton and colleagues examined various characteristics of the condition as it appeared in a community setting. They reviewed the medical records of all residents of Worcester, Massachusetts, diagnosed with possible deep vein thrombosis at all Worcester hospitals during 1999.

The team found that the age-adjusted rate of upper extremity deep vein thrombosis was 16 per 100,000 compared to 91 per 100,000 for lower extremity deep vein thrombosis.

Compared with patients with lower extremity deep vein thrombosis, patients with upper extremity clots were significantly more likely to have recently undergone central line placement (62%), a cardiac procedure, or ICU admission.

In fact, upper extremity patients were twice as likely to experience such an event during hospitalization than were those in the lower extremity group, the investigators report in the August issue of the American Journal of Medicine.

Short-term and 1-year recurrence and mortality rates did not differ between thrombosis groups, but the upper extremity patients were less likely to have pulmonary embolism on presentation or on follow-up.

The researchers conclude than many aspects of these groups differ and they call for further studies "to effectively target prophylaxis, improve diagnosis and optimize our treatment" for upper extremity thrombosis patients.