PURPOSE: Although performed inside a laboratory, attended polysomnography (PSG) has long been the gold standard for the diagnosis of sleep apnea. However, high costs and long wait times have led to the development of home-based portable monitoring devices. A bed sheet-shaped device called SD102 (Suzuken Co., Nagoya, Japan) has been developed, and its accuracy in evaluating sleep apnea is becoming evident. The purpose of this study was to confirm the accuracy of SD102 in evaluating sleep apnea and to investigate patient characteristics that may contribute to inaccurate test results in patients with suspected obstructive sleep apnea (OSA). METHODS: One hundred and eighty-nine patients simultaneously underwent PSG and portable monitoring by using a home sleep apnea testing (HSAT) device. A blinded, experienced technologist using the American Academy of Sleep Medicine criteria versions 2.1 and 2.3 scored the PSG data and HSAT device data, respectively. RESULTS: The respiratory event index (REI) by HSAT significantly correlated with the apnea-hypopnea index (AHI) by PSG (r = 0.974, p < 0.001). HSAT sensitivity, specificity, and positive and negative predictive values of 0.99, 0.83, 0.95, and 0.97, respectively. Body mass index and arousal index were significantly associated with the difference between REI from SD102 HSAT and AHI from PSG. CONCLUSIONS: This study demonstrates the good agreement between REI and AHI in patients with suspected OSA and suggests that understanding the limitations of different testing methods may help in the accurate detection of OSA.