Correlation analysis of the exercise test and hypokalemic periodic paralysis

Abstract

Objectve To explore the application of exercise test use in diagnosis of periodic paralysis. Methods Forty five cases of hypokalemic periodic paralysis were collected, and 40 health persons as control group. Both groups were measured serum potassium, serum creatase and thyroid function tests. All of them were taken exercise test (ET) and observe 50 minutes, measured before and after the test to seek the changes of compound muscle action potentials (CMAP), and its decreased more than 33% were considered abnormal. The application of exercise test use was analyzed in diagnosis of periodic paralysis. Results In patients with periodic paralysis, the incidence of ET positive was higher than the control subjects (80% vs 3.3%, P<0.001). This trend was significant after 20 minutes, such as 30 min [(37.8±13.2)% vs (6.2±3.2)%, P<0.01], 40 min [(40.3±17.6)% vs (3.2±1.9)%, P<0.01], 50 min [(45.26±19.9)% vs (-5.1±2.6)%, P<0.01]. Moreover, linear correlation analysis showed that the serum potassium had negative correlation with serum creatase (r=-0.483, P=0.024). ALL of symptoms improved after a week treatment, the ET positive rate was still higher in patients with periodic paralysis than the control subjects (80.0% vs 71.1%, P=0.824). Conclusions Exercise test was one of the important objective basis in the diagnosis of low potassium type periodic paralysis, and was not affected by treatment and testing time. Key words: Hypokalemic periodic paralysis/DI; Evoked potentials, motor; Electromyography