Neck Circumference Measurement for Surveillance and Early Detection of Hemorrhage After Thyroidectomy: A Diagnostic Accuracy Study.

Importance: Postthyroidectomy hemorrhage is a potentially life-threatening complication with no reliable noninvasive method of early detection. Objective: To evaluate the diagnostic accuracy of neck circumference measurement for early detection of postoperative hemorrhage after thyroidectomy. Design, Setting, and Participants: This diagnostic accuracy study at an academic teaching hospital used a prospective cohort of patients undergoing thyroid surgery from November 1, 2015, to January 31, 2018 (group 1), and a retrospective cohort of patients undergoing the same surgery from January 1, 2020, to September 30, 2021 (group 2). We performed repeated perioperative neck circumference measurements to evaluate the association of increased neck circumference with postthyroidectomy hemorrhage among patients at risk for hemorrhage. Main Outcomes and Measures: The primary end point was the diagnostic value of neck circumference measurement for detection of postthyroidectomy hemorrhage. Additionally, data on demographic information and risk factors for postthyroidectomy hemorrhage were examined. Data analyses were performed from November 1, 2021, to January 5, 2022. Results: The prospective cohort (group 1) comprised 60 patients (45 [75%] women) with a mean (SD) age of 52.2 (13.5) years; those who experienced a postthyroidectomy hemorrhage had a mean (SD) age of 57.4 (9.0) years. The retrospective cohort (group 2) comprised 353 patients (258 [73%] women) with a mean (SD) age of 55.3 (14.1) years; patients who experienced a postthyroidectomy hemorrhage had a mean (SD) age of 62.2 (10.0) years. In group 1, postoperative neck circumference increased by a median (range) of 5.0 (4.0 to 7.0) cm in patients with hemorrhage, and only 1.0 (-2.5 to 4.0) cm in patients with no postoperative bleeding (difference in the medians, 4.0 cm [95% CI, 3.0 to 5.5 cm]; effect size, 3.74 [95% CI, 2.6 to 4.9]). Defining a 7% or greater increase in neck circumference as the cutoff value for detecting postthyroidectomy hemorrhage showed a diagnostic sensitivity and specificity of 1.0 (95% CI, 0.48 to 1.0) and 0.86 (95% CI, 0.71 to 0.92), respectively. The retrospective validation also showed a difference in median (range) increase of postoperative neck circumference between patients with hemorrhage and those without-3.0 (0 to 6.0) cm vs 0.0 (-6.0 to 5.0) cm (difference in medians, 3.8 cm [95% CI, 3.0 to 4.9]; effect size, 1.63 [95% CI, 0.96 to 2.3]). Considering 12 false-positive and 332 correct-negative results, the diagnostic tool showed a sensitivity of 0.89 (95% CI, 0.51 to 0.99) and a specificity of 0.97 (95% CI, 0.94 to 0.98). Conclusions and Relevance: The findings of this diagnostic accuracy study suggest that neck circumference measurement is a feasible and easy-to-use diagnostic tool for routine clinical care to detect postthyroidectomy hemorrhage. A 7% or greater increase over the postoperative baseline neck circumference seems to be a reliable threshold for detecting postthyroidectomy hemorrhage. Neck circumference measurement should be used in combination with surveillance of clinical signs and symptoms.