A computerized Cheirometer has been developed to objectively assess grip strength indices (GSI) of normals and rheumatoid arthritis (RA) patients. The instrument consists of a hand-grip bladder, an LVDT pressure transducer (Schaevitz) interfaced through a 12 bit A/D converter to an Apple II + computer. Software has been developed for data acquisition, display and classification of measured GSI into moderately diseased and severely diseased and normal classes.
During the developmental phase of the instrument, it was noted that maximum pressure ( PM) and rate-of-rise (ROR) of pressure during the squeezing of the bladder were the most sensitive indices to distinguish and classify normal and patient hand-grip waveforms. The reproducibility of PM and ROR as useful GS indices was tested in 13 chronic RA patients in the morning, with two measurements per patient, within half-hour intervals. The results indicate that PM and ROR are stable indices with no significant variation between two measurements ( p < 0.05). A Bayes classifier program was developed to recognize and classify normal and pathological signatures of grip strength. The classifier accuracy was evaluated in 79 patients in the Rheumatology clinic at McMaster Hospital. A classification accuracy of 90 per cent was obtained in classifying normals and pathological subjects.