Background Remote pulmonary function testing with improved patient engagement is necessary for clinical decision-making in ALS (Geronimo 2019). Vital capacity stratification may allow identification of differential disease trajectories (Ackrivo 2019). Objectives Validate SVC using portable and conventional spirometry to determine feasibility and utility of pulmonary function test surveillance from home. Methods IRB-approved study is conducted at two ALS Centers where respiratory technologist-coached SVC using FDA-approved portable spirometer (MIR Spirobank Smart), mobile app (ZephyRx) and conventional laboratory spirometer (Viasys, Viaire) was followed with Telespirometry every 2 weeks [ median = 9; range 0-22 patient-weeks ]. Results Longitudinal portable and conventional SVC measurements showed acceptability rate of 94% (N=205) and 69.4% (N=34) respectively. Bland Altman analysis in-clinic upright SVC (N=18) mean difference =-0.684% predicted;95% LoA = -11.816% to 15.447% whereas in-clinic supine SVC (N=14) mean difference = 6.78% predicted;95% LoA = -8.83% to 22.39% (conventional – portable). Telespirometry identified 7/12 (58%) patients without NonInvasive Ventilation (NIV) vs 2/6 (33%) patients with NIV had SVC drops by > 10% predicted [NS P=0.31; chi-square]. Overall, participants had median SVC drop per interval in no NIV patients = -15 % predicted (range: -20 to +20) and in NIV patients = -2 % predicted (range: -16 to + 6) [NS P=0.47; unpaired t test]. Discussion SVC measured with portable spirometry in upright and supine positions is validated as accurate with conventional clinic spirometry. Telespirometry yielded a much higher acceptability rate than conventional spirometry due to clinical usability (Graham 2019) in the first twenty research participants followed for a mean of 2.42 (SD1.64) person-months. Subjects already on NIV more frequently performed supine spirometry. SVC drops trended to be less common on NIV in this pilot study. Further data acquisition is ongoing to determine how augmenting Telespirometry, based on SVC stratification, leads to more timely pulmonary treatment interventions.