Systematic review Systematic review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia O. Edafe 1 , R. Antakia 1 , N. Laskar 2 , L. Uttley 3 and S. P. Balasubramanian 1 1 Department of Oncology, 2 The Medical School and 3 School of Health and Related Research, University of Sheffield, Sheffield, UK Correspondence to: Mr O. Edafe, Department of Oncology, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, UK (e-mail: ovieedafe@hotmail.co.uk) Background: Hypocalcaemia is common after thyroidectomy. Accurate prediction and appropriate management may help reduce morbidity and hospital stay. The aim of this study was to perform a systematic literature review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia. Methods: A systematic search of PubMed, EMBASE and the Cochrane Library databases was undertaken, and the quality of manuscripts assessed using a modified Newcastle–Ottawa Scale. Results: Some 115 observational studies were included. The median (i.q.r.) incidence of transient and permanent hypocalcaemia was 27 (19–38) and 1 (0–3) per cent respectively. Independent predictors of transient hypocalcaemia included levels of preoperative calcium, perioperative parathyroid hormone (PTH), preoperative 25-hydroxyvitamin D and postoperative magnesium. Clinical predictors included surgery for recurrent goitre and reoperation for bleeding. A calcium level lower than 1·88 mmol/l at 24 h after surgery, identification of fewer than two parathyroid glands (PTGs) at surgery, reoperation for bleeding, Graves’ disease and heavier thyroid specimens were identified as independent predictors of permanent hypocalcaemia in multivariable analysis. Factors associated with transient hypocalcaemia in meta-analyses were inadvertent PTG excision (odds ratio (OR) 1·90, 95 per cent confidence interval 1·31 to 2·74), PTG autotransplantation (OR 2·03, 1·44 to 2·86), Graves’ disease (OR 1·75, 1·34 to 2·28) and female sex (OR 2·28, 1·53 to 3·40). Conclusion: Perioperative PTH, preoperative vitamin D and postoperative changes in calcium are biochemical predictors of post-thyroidectomy hypocalcaemia. Clinical predictors include female sex, Graves’ disease, need for parathyroid autotransplantation and inadvertent excision of PTGs. Presented to the 33rd Annual Meeting of the British Association of Endocrine and Thyroid Surgeons, Rome, Italy, October 2013 Paper accepted 25 October 2013 Published online 9 January 2014 in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9384 Introduction Hypocalcaemia following bilateral thyroidectomy is com- mon. The British Association of Endocrine and Thyroid Surgeons audit 1 reported rates of 27·4 and 12·1 per cent for transient and permanent post-thyroidectomy hypocal- caemia respectively. Direct injury to, or devascularization of, the parathyroid glands (PTGs) is generally accepted as the most common reason for post-thyroidectomy hypo- calcaemia. Accurate prediction of risk has the potential to influence management strategies and could possibly reduce the risk of this complication. This systematic review was carried out with the aim of identifying reported predictors of transient and permanent hypocalcaemia in patients undergoing bilateral thyroid surgery. The key objectives were to identify predictors of transient and permanent post- thyroidectomy hypocalcaemia, and to estimate, if possible, the strength of association between reported predictive factors and transient and permanent post-thyroidectomy hypocalcaemia. Methods A literature search of PubMed (14 August 2012), EMBASE (11 October 2012) and the Cochrane Library (10 August 2012) was performed to retrieve articles published between 1 January 1990 and 30 July 2012. The following terms were used in the search text fields: ‘low calcium’  2014 BJS Society Ltd BJS 2014; 101: 307–320 Published by John Wiley & Sons Ltd