Handgrip strength measured by a dynamometer connected to a smartphone: a new applied health technology solution for the self-assessment of rheumatoid arthritis disease activity

Rheumatology 2016;55:897–901 doi:10.1093/rheumatology/kew006 Advance Access publication 10 February 2016 RHEUMATOLOGY Concise report Handgrip strength measured by a dynamometer connected to a smartphone: a new applied health technology solution for the self-assessment of rheumatoid arthritis disease activity Objective. The aim was to analyse the accuracy of a hand dynamometer connected to a smartphone to assess RA disease activity through the measurement of handgrip strength (HGS). Methods. Eighty-two RA patients participated in this prospective study. Three types of HGS were assessed: power (Po), pinch (Pi) and tripod (T). An interactive mobile application was developed to capture grip measures. A unilinear regression analysis between HGS and DAS28 was performed. A multivariate regression analysis to identify independent variables related to HGS was also conducted. Results. Sixty-three patients (76.8%) were female. Mean age was 61.3 years. At baseline, a negative correlation between the three HGS measures and DAS28 score was found, as follows: Po, r = 0.65 (95% CI: 0.76, 0.51, P < 0.001); Pi, r= 0.42 (95% CI: 0.59, 0.23, P < 0.001); and T, r = 0.47 (95% CI: 0.63, 0.29, P < 0.001). In a longitudinal analysis of 32 patients, a negative correlation between
Po grip and
DAS28 was found (r = 0.76, 95% CI: 0.88, 0.56). Po grip was independently correlated with male sex (95% CI: 1.49, 4.14, P = 0.002), whereas variables inversely correlated with Po grip were disease duration (95% CI: 2.71, 1.34, P = 0.03), patient global assessment (95% CI: 2.41, 1.1, P < 0.001) and CRP level (95% CI: 3.56, 1.08, P < 0.001). Conclusion. HGS assessed by a hand dynamometer connected to a smartphone represents an innovative health technology solution that could prompt the self-assessment of RA disease activity in an outpatient setting. Key words: hand strength, rheumatoid arthritis, biomedical technology, telemedicine Rheumatology key messages . Assessment of handgrip strength in RA is strongly correlated with DAS28 score. . Handgrip strength is independently correlated with two other markers of RA disease activity; patient global assessment and CRP level. . Handgrip strength assessed by a personal device represents a self-assessment instrument of RA disease activity. Introduction 1 Clinical Immunology and Osteoarticular Diseases Therapeutic Unit, Lapeyronie University Hospital, Montpellier, 2Bodysens, Nimes and 3 Optimal Medicine, Montpellier, France Submitted 3 May 2015; revised version accepted 16 January 2016 *Correspondence to: Yves-Marie Pers, Clinical Immunology and Osteoarticular Diseases Therapeutic Unit, Lapeyronie University Hospital, 371, Avenue du doyen Gaston Giraud; 34295 Montpellier, France. E-mail: Remarkable progress has been achieved in the management of patients with RA. Biologic targeted therapies together with the application of treat-to-target strategy have substantially improved the quality of life and prognosis of patients [1, 2]. One of the remaining issues is the development of reliable, user-friendly self-assessment tools [3, 4] that could offer close surveillance of disease activity. ! The Author 2016. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: CLINICAL SCIENCE Abstract Francisco Espinoza1, Pierre Le Blay1, Denis Coulon2, Sylvain Lieu2, Janet Munro3, Christian Jorgensen1 and Yves-Marie Pers1 Francisco Espinoza et al. Materials and patients Patients Patients were prospectively included between December 2013 and June 2014 at the Clinical Immunology and Osteoarticular Diseases Therapeutic Unit of Lapeyronie University Hospital (Montpellier, France). All patients fulfilled the 2010 ACR/EULAR criteria for RA [16]. A pilot study with 15 patients was previously conducted to assess the safety, feasibility and reliability of the device and to establish the conditions of test (data not published). Patients with the following conditions were excluded: surgery below the humerus or any surgical procedure in the last 5 years deemed to have a detrimental effect on grip; suspicion of CTS; other peripheral neurological deficit; muscular disorders; and chronic tendon dysfunction. The study did not interfere with patient treatment. Demographic data were collected from medical records. The following parameters were recorded: age, sex, disease duration, BMI, presence of erosions, tender joint count, swollen joint count, patient global assessment (PGA), duration of morning stiffness, RF or ACPA positivity, ESR, CRP level, treatment with prednisone, biologics (b) and synthetic (s) DMARDs. The DAS28 was used to assess RA disease activity. Laboratory tests were obtained within 3 days of grip assessment. The study was approved by the local ethical committee (Comité de Protection des Personnes, CHU Montpellier, registered code 2014-A00824-43). Written consent was obtained from each patient. HGS: measures and standard operation procedure The HGS test was performed in the morning during a routine hospital consultation. In order to keep the researcher blinded, an alternative investigator who did not participate in the recollection of clinical and biological data helped the patient to perform the grip test. Three types of grips were assessed: power grip (Po), pinch grip (Pi) and tripod grip (T). Po was measured between the partly flexed fingers and the palm while the thumb applied counter-pressure. Pi was measured between thumb pulp and second digit pulp, and T was measured between thumb pulp and second and third digit pulp (supplementary Fig. S1, available at Rheumatology Online). Only the dominant hand was evaluated. Measures were made in a quiet room. Patients were 898 tested while sitting, with the elbow flexed at 90 degrees and the forearm resting on a table in a comfortable position. The evaluator checked all these conditions in agreement with previous work of Mathiowetz et al. [17]. Patients were asked to perform three maximal voluntary contractions of 5 s each; one for each type of grip. In order to standardize the procedure, the system included an audiovisual guide to assist the patient during the test. The application recorded and backed up each test. Rest breaks of 30 s were completed between each effort. Altogether, patients performed nine grip assessments. Dynamometer Grip was assessed using a dynamometer HD-BTA (Vernier Software & Technology, Beaverton, OR, USA). This instrument was connected to a smartphone, and a mobile application was created setting an interface between the mobile and the dynamometer (Bodysens Society, Nimes, France). Variables recorded were as follows: maximal grip (Po-max), average power grip (Po-av), maximal (Pi-max) and average pinch grip (Pi-av), maximal (T-max) and average tripod grip (T-max). Data were stored in a private electronic database and were recovered by the investigators afterwards. All values were expressed in kilograms. S (...truncated)