hypocalcaemia following CND occurs in 14% to 40% of cases.8. CND is defined as complete removal of the lymph nodes within the central neck compartment, ...
Clinical Endocrinology (2016)
doi: 10.1111/cen.13082
ORIGINAL ARTICLE
Incidence of permanent hypocalcaemia after total thyroidectomy with or without central neck dissection for thyroid carcinoma: a nationwide claim study Gi Hyeon Seo*, Young Jun Chai†,‡, Hyung Jin Choi§ and Kyu Eun Lee‡,¶ *Health Insurance Review and Assessment Service, †Department of Surgery, Seoul National University Boramae Medical Center, Dongjak-gu, ‡Cancer Research Institute, Seoul National University College of Medicine, §Department of Anatomy, Seoul National University College of Medicine, and ¶Department of Surgery, Seoul National University Hospital and College of Medicine, Jongno-gu, Seoul, Korea
Introduction Summary Objective Permanent hypocalcaemia is the most common and serious complication after total thyroidectomy (TT). This study examined the impact of central neck dissection (CND) and institutional volume on rates of permanent hypocalcaemia by analysing data held in the nationwide claim database of South Korea. Design Data from patients who underwent TT due to thyroid carcinoma from 2007–2013 were obtained from the Health Insurance Review and Assessment Service database. Of these, patients prescribed more than 1000 mg of elemental calcium for more than 288 days during the first 360 days postsurgery were defined as having permanent hypocalcaemia. Results In total, 192 333 patients (32 988 male and 159 345 female) were eligible for analysis. Of these, 52 707 (274%) underwent TT alone and 139 626 (726%) underwent TT plus CND. The incidence of permanent hypocalcaemia was greater in the TT plus CND group than in the TT alone group (54% vs 46%, P < 0001). The age- and sex-adjusted risk for permanent hypocalcaemia in the TT plus CND group was 120 (P < 0001). CND did not raise the rates of permanent hypocalcaemia in institutes with a low volume of annual cases (80% (288) of the 360 days immediately after admission for surgery; and (ii) the mean amount of daily calcium exceeded 1000 mg of elemental calcium. To evaluate the exact number of calcium prescription days during the first 360 days after admission for surgery, the number of days beyond the first 360 was excluded. When evaluating the calcium dose, we analysed all types of claim code, including calcium carbonate, citrate tablets and calcium/vitamin D complexes, that are available in South Korea. We calculated that calcium carbonate and calcium citrate are 400% and 211% elemental calcium, respectively. Statistical analysis Continuous variables were expressed as the mean with standard deviation, and the groups were compared using Student’s t-test.
Categorical variables were expressed as the number and percentage and compared using the chi-square test. Logistic regression was used to assess relative risk. All statistical analyses were performed using R software, version 3.2.2 (R Foundation for Statistical Computing, Vienna, Austria). Differences were considered significant at P < 005.
Results A total of 192 333 patients (32 988 male and 159 345 female) were eligible for analysis (Table 1). Of these, 52 707 (274%) underwent TT alone and 139 626 (726%) underwent TT plus CND due to thyroid carcinoma. The mean age of the TT alone and TT plus CND groups was 488 118 and 485 118 years, respectively. The incidence of permanent hypocalcaemia in the TT plus CND group was greater than that in the TT alone group (54% vs 46%, respectively; P < 0001). The age- and sex-adjusted risk for permanent hypocalcaemia for the TT plus CND group compared with that for the TT alone group was 120 (115–126) (P < 0001). The mean amount of daily elemental calcium for the patients with permanent hypocalcaemia in the TT alone group was 1439 559 mg and that for the TT plus CND group was 1395 440 mg. Table 2 demonstrates the annual incidence of permanent hypocalcaemia in the TT alone and TT plus CND groups. The incidence of permanent hypocalcaemia according to the annual institutional volume of thyroidectomies from 2007 to 2013 is shown in Table 3. CND did not increase the rate of permanent hypocalcaemia when performed in institutes with
