The value of the isometric hand-grip test--studies in various autonomic disorders

Time-related methodological differences have confounded the value of isometric hand-grip (IHG) exercise as a test of sympathetic function. This study examines the blood pressure response to IHG in 71 normal subjects and 76 dysautonomic patients and compares it with the tilt table test. All participants were supine and performed IHG at 30% of maximum contraction for 5 min. Change in diastolic blood pressure (DBP) was the most sensitive and specific measurement in diagnosing abnormals. The multivariate group by time (1-5 min) effect was significant (F = 10.14, p < 0.001) with 5 min as the most important time measurement (Wilk's lambda = 0.70, p < 0.001). The DPB rise for normals was 25.15 +/- 1.31 mmHg (mean +/- SE), range 22.55-27.76 mmHg, with a sensitivity of 78.95% and a specificity of 71.83%. A multivariate analysis of variance showed intraindividual reproducibility of nine normals over four trials (F = 0.950, p > 0.25). Gender and grip strength were additional important variables. In comparison, the tilt table test demonstrated a sensitivity of 82.76% and a specificity of 73.68%. Isometric hand-grip is therefore a specific, sensitive, reproducible, simple and non-invasive test of sympathetic function with relatively well-studied reflex pathways. Its sensitivity and specificity compare favourably with the tilt table test. It should be incorporated in routine autonomic testing.