Development of a standardized pulse-controlled ergometry test for diagnosing and investigating cholinergic urticaria

Cholinergic urticaria (CholU) is a common condition in which active or passive warming leads to development of pinpoint wheals, flares and itch.

To develop a standardized protocol for diagnosing CholU and measuring trigger thresholds, independent of patients' fitness levels.

Ten CholU patients and matched healthy controls underwent pulse-controlled incremental ergometry for 30 min (stationary bicycle) increasing their pulse rate by 15 beats every 5 min. Non-invasive, heat-flux double-sensor and conventional electronic thermometers measured core and skin surface temperatures from which mean body temperature (MBT) was calculated. The time of onset of sweating (starch-iodine test) and symptoms (whealing) were recorded.

All individuals completed the ergometry protocol without difficulty. All CholU patients but no controls developed wheals. The time to whealing correlated inversely with disease severity. In four patients MBT increased <0.5°C and in two whealing occurred at a temperature lower than at the start of exercise. Onset of symptoms correlated with the time of sweating.

Pulse-controlled ergometry is sensitive and specific for diagnosing CholU and investigating trigger thresholds and disease mechanisms. Our results refute the hypothesis that a rise in MBT is the critical trigger for CholU while sweating appears to have the central role.