Prediction of hypocalcemia after using 1- to 6-hour postoperative parathyroid hormone and calcium levels: an analysis of pooled individual patient data from 3 observational studies

Assessing Postoperative Phosphate and Calcium/Phosphate Ratio as Surrogates for Parathyroid Hormone Following Total Thyroidectomy

OBJECTIVE

Evaluate utility of postoperative phosphate and calcium/phosphate ratio (Ca/P) as surrogates for parathyroid hormone (PTH) following total thyroidectomy.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary care hospital.

METHODS

We retrospectively reviewed patients 18 years or older who underwent total thyroidectomy in a tertiary care hospital by a single surgeon from 2015 through 2021. Patients with incomplete data, pre-existing hypoparathyroidism, vitamin D deficiency, or renal failure were excluded. All patients had PTH drawn within 4 hours of surgery and serum calcium, albumin, and phosphate levels on postoperative Day 1. Corrected calcium was used to calculate a Ca/P. Receiver operating characteristic (ROC) curves were generated to compare phosphate level or Ca/P with PTH. Each possible surrogate was assessed relative to PTH cutoffs of less than 5, 10, 15, and 20 pg/mL. A good screening test was defined as having an area under the curve (AUC) greater than 0.8.

RESULTS

A total of 185 patients underwent total thyroidectomy with 1 fellowship-trained otolaryngologist. Most patients were female (62%), median age 48 years. Most surgeries were performed for cancer (68%). Six (3.2%) patients required IV calcium supplementation and 2 (1.1%) required readmission for symptomatic hypocalcemia. ROC curves comparing phosphate and Ca/P to PTH at the listed cutoffs demonstrated AUC ranging from 0.55 to 0.66 and 0.61 to 0.79, respectively. None met the threshold for a good screening test.

CONCLUSION

Postoperative phosphate and Ca/P ratio are not surrogates for PTH levels following total thyroidectomy. More research is needed to identify cost-effective strategies for postoperative calcium monitoring in patients undergoing total thyroidectomy.

LEVEL OF EVIDENCE

Retrospective cohort study.

Predictive value of postoperative day 1 parathyroid hormone levels for early and late hypocalcaemia after thyroidectomy

PURPOSE

Early parathyroid hormone (PTH) levels after total thyroidectomy can predict patients at low risk of hypocalcaemia who can be discharged early without calcium supplementation. For centres without facility to perform early PTH levels, PTH levels sent on the first postoperative day (POD1) may be an alternative. However, there is less data regarding optimal cut-off PTH levels for POD1 discharge.

METHODS

Retrospective review of prospective database of thyroid operations between September 2009 and February 2020 at tertiary referral centre. Main outcome measure was symptomatic hypocalcaemia.

RESULTS

Five hundred seventy patients undergoing total (521) or completion thyroidectomy with POD1 PTH levels available were included. Among patients with POD1 PTH levels ≥ 20 pg/ml and POD1 calcium ≥ 2.0 mmol/l, the incidence of symptomatic hypocalcaemia was 1% (3/300), and need for intravenous calcium 0.3% (1/300). For POD1 PTH levels 15-19 pg/ml and POD1 calcium ≥ 2.0 mmol/l, the incidence of symptomatic hypocalcaemia and need for intravenous calcium was 5.4% (3/55). For PTH levels 10-14 pg/ml and calcium ≥ 2.0 mmol/l, the incidence of symptomatic hypocalcaemia and need for intravenous calcium was 11.7% (7/60). The risk of permanent hypoparathyroidism was < 1% for POD1 PTH levels ≥ 15 pg/ml; 5.4% for levels 10-14 pg/ml; and 19.8% for levels < 10 pg/ml.

CONCLUSIONS

POD1 PTH levels ≥ 15 pg/ml along with calcium ≥ 2.0 mmol/l are associated with low risk of symptomatic hypocalcaemia, and represent a safe criterion for discharge of most patients without calcium supplementation. For certain patient groups, a higher threshold of 20 pg/ml could be considered.

Predicting risk factors of postoperative hypocalcemia after total thyroidectomy: is safe discharge without supplementation possible? A large cohort study

PURPOSE

With increasing economic pressures to shorten the length of hospital stay, there has been much recent interest in studying risk factors for the development of postoperative hypocalcemia after total thyroidectomy. The aim of this study was to investigate whether serum calcium and/or PTH levels can predict post-thyroidectomy hypoparathyroidism.

METHODS

From January to December 2014, 477 consecutive patients undergoing total thyroidectomy were included. Corrected calcemia and PTH were systematically performed on postoperative day 1/(POD1). Symptomatic patients were treated on POD1 or POD2 with calcium and vitamin D.

RESULTS

Sixty-eight patients (14.25%) were treated for postoperative hypocalcemia. No patients with calcemia ≥ 2.16 mmol/l and PTH ≥ 1.9 pmol/l were supplemented and therefore were safely discharged on POD1 (specificity = 100%). All patients with calcemia ≤ 1.89 mmol/l were treated regardless the PTH values (n = 10) (specificity = 100%). For calcium value between 1.9 and 2.16 mmol/l with a PTH > 4.7 pmol/l, nobody was treated. With a calcemia between 1.9 and 2.16 mmol/l and a PTH > 1.9 pmol/l, 44 patients did not develop any symptom. ROC curve analysis showed that combination of Cac = 2.16 mmol/l and iPTH = 4.7 pmol/l provided a sensitivity of 97.06% and a specificity of 76.53% (p < 0.0001). We therefore propose an algorithm that would allow to 70% of patients could have been discharged on POD1 without risk of hypocalcemia or overtreatment.

CONCLUSION

Combination of corrected calcemia and PTH on POD1 can efficiently predict hypocalcemia and be integrated into clinical practice for personalizing lengths of hospitalization and appropriate treatment.

TRIAL REGISTRATION

ClinicalTrials.gov PRS. Unique Identifying number or registration ID: NCT04372225.

The significance of Hashimoto's thyroiditis for postoperative complications of thyroid surgery: a systematic review and meta-analysis

INTRODUCTION

Hashimoto's thyroiditis (HT) is one of the most common immune-mediated diseases. It makes thyroid surgery more complicated and difficult because there may be adhesions between the thyroid gland and surrounding structures. However, it is still controversial whether HT patients carry a high risk for postoperative complications of thyroid surgery. The purpose of this study was to investigate the significance of HT for the postoperative complications of thyroid surgery.

METHODS

A search for studies assessing the postoperative complication risks of HT patients compared with that of patients with benign nodules (BNs) was performed in PubMed, EMBASE and Web of Science. Nine studies (20,118 cases, 1,582 cases of HT and 18,536 cases of BN) were identified, and the data from the relevant outcomes were extracted and analysed.

RESULTS

There were no significant differences between the HT group and BN group in recurrent laryngeal nerve palsy (RLNP) and permanent hypoparathyroidism (PHP). The rate of transient hypocalcaemia (THC) was significantly higher in the HT group (16.85%) than in the BN group (13.20%).

CONCLUSIONS

The meta-analysis showed that HT only increased the risk of the postoperative complication THC compared to BN. Understanding the significance of HT in postoperative hypoparathyroidism after thyroid surgery would help clinicians perform sufficient preoperative (and postoperative) assessments and to optimise surgical planning.

Morbidity following thyroid surgery: acceptable rates and how to manage complicated patients

PURPOSE

The endocrine surgeon and the endocrinologist should standardize how they deal with patients with an indication for thyroidectomy, as the road to surgery starts well before the operation itself. The patient should be thoroughly informed about where and how surgery will be performed, the postoperative improvements that can be expected, and the possibility and incidence of relevant complications. This short review aims at identifying the most common postoperative issues after thyroidectomy, with the relevant therapeutic suggestions.

METHODS

A revision of studies reporting the morbidity of thyroid surgery, involving the largest numbers of patients.

RESULTS

It has been clearly demonstrated that the outcome of thyroid surgery is significantly better when the procedure is performed by an experienced surgeon. Thus, the number of thyroidectomies performed by a surgeon should drive the endocrinologist when referring a patient.

CONCLUSIONS

Despite the surgeon's experience, thyroidectomy is burdened by a relatively high rate of postoperative issues ranging from less severe ones to others causing significant changes in the patient's quality of life. Minor, non-invalidating symptoms have been described in 40% of patients after thyroidectomy (e.g. hoarseness, mild dysphagia, some degree of voice alteration); however, these symptoms usually resolve within a few months of surgery, with or without early treatment. On the other hand, major postoperative complications are observed in a limited number of patients, but in these cases early diagnosis is important to provide the most appropriate postoperative treatment, and thus hasten full recovery or at least achieve the greatest possible improvement.

Hypocalcemia after thyroidectomy: iPTH levels and iPTH decline are predictive? Retrospective cohort study

Background

Hypocalcemia is the most common complication of thyroid surgery. The aim of this study was to determine the early predictive factors of postoperative hypocalcemia and to analyze their efficiency.

Methods

We performed a retrospective study of 345 consecutive patients who underwent total thyroidectomy at the Endocrine Surgery Department (Policlinico G. Rodolico Hospital of Catania) between January 2011 and November 2013. We measured serum intact parathormone (iPTH) levels preoperatively and 4 h after surgery. The threshold values of hypocalcemia for iPTH levels and iPTH relative decline were obtained by receiver operating curves (ROC) analysis.

Results

The incidence of hypocalcemia was 32.2% (111 of 345 patients). Our statistical analysis revealed that hypocalcemia rate was strongly correlated with the lower iPTH values and greater iPTH decline (P < 0.001). The threshold enabling prediction of hypocalcemia were 12,5 pg/mL for iPTH and 55,7% for relative iPTH decline. Patients with iPTH <12,5 pg/mL developed hypocalcemia in 58.6% of cases while those with iPTH ≥12,5 pg/dl in 18.8%. Among 175 patients with iPTH relative decline greater than 55,7% hypocalcemia was diagnosed in 91 cases (52%), while other 170 patients with iPTH relative decline less than 55,7% developed hypocalcemia only in 20 cases (11,7%).

Conclusions

The decreased iPTH levels and increased iPTH relative decline resulted to be an accurate predictive factors of postoperative hypocalcemia. The early administration of Calcium and vitamin D in the high-risk patients should be put on in order to prevent the symptoms of hypocalcemia and to reduce the costs and duration of hospitalization.

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Predictive factors of postoperative hypocalcemia.

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Retrospective study of 345 patients.

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The threshold were iPTH 12,5 ng/L and iPTH decline 55,7%.

Parathyroid Hormone Assays following Total Thyroidectomy: Is There a Predictive Value?

OBJECTIVES

Parathyroid hormone (PTH) is a risk marker for hypoparathyroidism (hypoPTH). This study aimed to determine the predictive values of early PTH assays carried out at the moment of skin closure (PTH SC), to establish a treatment algorithm, identifying two threshold values. We assessed the reproducibility of this approach with two different immunoassay kits (hypoPTH) after total thyroidectomy, but its practical application is not consensual.

STUDY DESIGN

We conducted a prospective descriptive study, including all patients who underwent a total thyroidectomy between March 2012 and November 2013. Postoperative PTH SC levels, corrected calcium on postoperative days, and occurrence of hypoPTH symptoms were collected.

RESULTS

Of 257 patients, the rate of hypoPTH was 20%. Threshold values to obtain a 100% positive predictive value to identify patients for whom hypoPTH was absolutely certain were: PTH SC <7 ng/L for the Roche kit and PTH SC <4 ng/L for the Beckman-Coulter kit. Threshold values to obtain a 100% negative predictive value to identify patients for whom the absence of hypoPTH was absolutely certain were: PTH SC ≥19 ng/L for the Roche kit and PTH SC ≥9 ng/L the Beckman-Coulter kit.

CONCLUSIONS

A single serum PTH sampled at skin closure is a reliable test to predict hypoPTH after a total thyroidectomy. The use of a threshold based on a 100% negative predictive value enables patients with no risk of hypoPTH to be safely discharged within the first 24 h postoperatively without unnecessary calcium and vitamin treatment. This medication can be given promptly to patients at risk of hypoPTH to limit the occurrence of hypocalcaemia.

Risk factors for hypocalcemia and hypoparathyroidism following thyroidectomy: a retrospective Chinese population study

Background

Hypocalcemia is one of the most common postoperative complications following thyroid surgery in clinical practice. The occurrence of hypocalcemia is mainly attributed to hypoparathyroidism when parathyroid glands are devascularized, injured, or dissected during the surgery. The aim of this study was to analyze the risk factors for hypocalcemia and hypoparathyroidism following thyroidectomy.

Patients and methods

A total of 278 patients who underwent thyroid surgery were analyzed retrospectively. Univariate analysis and multivariable logistic regression were performed to discover the risk factors for hypocalcemia and hypoparathyroidism.

Results

Postoperative hypocalcemia occurred in 76 (27.3%) patients and hypoparathyroidism occurred in 42 (15.1%) patients. Seven factors were significantly related to the presence of postoperative hypocalcemia, namely, age (P=0.049), gender (P=0.015), lateral lymph node dissection (P=0.017), operation type (P<0.001), preoperative parathyroid hormone (PTH) level (P=0.035), operation time (P=0.001), and applying carbon nanoparticles (CNs; P=0.007). Our result revealed that gender (P=0.014), lateral lymph node dissection (P=0.038), operation type (P<0.001), operative time (P<0.001), and applying CNs (P=0.001) had a significant correlation with postoperative hypoparathyroidism.

Conclusion

These findings were crucial for guiding surgeons to prevent the occurrence of hypocalcemia and hypoparathyroidism.

[Intraoperative parathyroid hormone measurement is the best predictor of postoperative symptomatic hypocalcemia]

BACKGROUND

The goal of this study is to evaluate risk factors for transient postoperative hypocalcemia (HC) and to define cutoff values for perioperative parathyroid hormone (PTH) and calcium parameters (Ca) to reduce the morbidity of symptomatic HC.

MATERIALS AND METHODS

At our tertiary referral hospital (Luzerner Kantonsspital, Switzerland), a total of 353 patients underwent total thyroidectomy between 2006 and 2013 and were analyzed retrospectively in terms of HC risk. The serum values of calcium and PTH were measured at strictly defined time intervals, and patients' symptoms and the necessity of treatments were determined from patients' charts.

RESULTS

The prevalence of transient postoperative HC was 43%; however, only 10% of patients were symptomatic. Significant risk factors for serum and symptomatic HC were calcium values (pre-, intra-, 4 h and 1 d postoperative), PTH values (intraoperative, 4 h and 1 d postoperative), and PTH decline. Interestingly, preoperative PTH values, patient age, weight of the thyroid gland, diagnosis, and sex were not significant risk factors. In the ROC analysis ('receiver operating characteristics'), calcium measurement 4 h postoperatively showed the best predictive ability for detecting serum HC, whereas intraoperative PTH measurements were predictive for symptomatic HC.

CONCLUSION

Calcium and PTH values as well as PTH decline are significant risk factors for postoperative HC. Preoperatively, only calcium measurement is prognostically significant. Intraoperative PTH measurement is the most reasonable and sensitive factor for early recognition of temporary postoperative HC in the clinical setting.

Early prediction of hypocalcemia following thyroid surgery. A prospective randomized clinical trial

PURPOSE

The aim of this randomized-controlled trial was to validate the results of a previous prospective single-cohort observational study conducted in the same surgical unit regarding the use of concomitant intact parathyroid hormone (iPTH) and serum calcium measurement in predicting hypocalcemia after total thyroidectomy.

METHODS

From January 2014 to January 2015, 150 patients underwent total thyroidectomy in our department and were randomized into two groups. The experimental group was submitted to iPTH assay 6 h after surgery while the control group was submitted to a daily assay of serum calcium and phosphorus. Sensitivity and specificity of different serum measurements have been calculated using the receiver-operator characteristics (ROC) curve.

RESULTS

The prevalence of hypocalcemia was 14.25% in both groups. The assay of iPTH 6 h after surgery combined with the serum calcium assay 24 h after surgery yielded the highest diagnostic accuracy in predicting hypocalcemia using ROC curves, with 100% sensitivity and 100% specificity.

CONCLUSIONS

According to our previous study, the combined measurement of iPTH 6 h after surgery and of serum calcium 24 h after surgery are highly predictive of early postoperative hypocalcemia. These results are important in selecting the patients eligible for early discharge and those who need calcium and vitamin D supplementation.

Clinicopathological risk factors and biochemical predictors of safe discharge after total thyroidectomy and central compartment node dissection for thyroid cancer: a prospective study

To determine the clinicopathological risk factors and reliable biochemical predictors of the development of hypocalcemic symptoms after total thyroidectomy on the basis of serum calcium and intact parathyroid hormone (PTH) levels measured 1 hour after surgery, a prospective study was performed on 817 patients who underwent a total thyroidectomy with central compartment node dissection (CCND) due to well-differentiated thyroid cancer. We evaluated the correlations between hypocalcemic symptom development and clinicopathological factors. And the predictability for hypocalcemic symptom development of intact PTH cut-offs (<10 pg/mL and <20 pg/mL, resp.) according to serum calcium level subgroup was analyzed. Female gender (P < 0.001) was the only independent risk factor for hypocalcemic symptom development in multivariate regression analysis. The negative predictive value (NPV) of intact PTH, signifying nondevelopment of hypocalcemic symptoms, was higher than the positive predictive value (PPV) which signified development of hypocalcemic symptoms. In addition, when we applied the different adoption of the intact PTH cut-off according to serum calcium level, we could obtain more increased NPVs. A female gender and the application of more specific cut-offs for intact PTH according to the serum calcium levels measured 1 hour after surgery may help the patients to be more safely discharged.

Predictable criteria for selective, rather than routine, calcium supplementation following thyroidectomy

OBJECTIVES

To identify patients at risk for symptomatic hypocalcemia and to make recommendations for safe, selective calcium supplementation.

DESIGN

Retrospective review of consecutive patients undergoing thyroidectomy. Patients were divided into 2 groups. Group 1 (the "high-risk/calcium-yes" group) included patients who were found to have (1) postoperative symptoms of hypocalcemia (ie, tingling and numbness), (2) any postoperative serum calcium level of less than 7 mg/dL, or (3) a parathyroid hormone level of less than 3 pg/mL on postoperative day 1. Group 2 (the "low-risk/calcium-no" group) included all other patients. Demographic, operative, biochemical, and pathologic data, as well as postoperative calcium supplementation data, were recorded. Trends in serum calcium level and parathyroid hormone level were analyzed during the immediate postoperative period to identify specific factors unique to group 1.

PATIENTS

A total of 156 patients who underwent a thyroidectomy.

SETTING

Tertiary care center.

RESULTS

Of the 156 patients reviewed, 78% were female, 70% had a malignant disease, and the median age at operation was 50 years. Thirty-four patients (22%) were in group 1, and 122 patients (78%) were in group 2. Twenty-nine (19%) patients had a parathyroid hormone level of less than 3 pg/mL within 24 hours after a thyroidectomy. Patients who underwent a central neck dissection (P = .001), had malignant disease (P = .01), or had a documented removal of the parathyroid gland (with or without autotransplantation) at operation (P = .013) were most likely to be classified into group 1. Forty-two percent of patients in group 2 had either a parathyroid hormone level of less than 6 pg/mL or a serum calcium level of less than 8 mg/dL on postoperative day 1, but all patients in group 1 who were symptomatic met these parameters.

CONCLUSION

Limiting supplementation to patients with a parathyroid hormone level of less than 6 pg/mL or a serum calcium level of less than 8 mg/dL on postoperative day 1 may eliminate unnecessary calcium/vitamin D intake, phlebotomy, and follow-up assessments in up to 58% of patients undergoing thyroidectomy. Validation is required in a prospective setting.