Postthyroidectomy complications and associated factors retropective study
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Retrospective Study Protocol
Title
Post-thyroidectomy complications and associated factors: a retrospective cohort study at [Hospital Name], [City/Country]
1. Background and rationale
Thyroidectomy is a common operation for benign thyroid disease, hyperthyroidism, compressive goiter, and thyroid malignancy. Although generally safe, it may cause complications ranging from transient biochemical hypocalcemia to life-threatening postoperative neck hematoma. Important complications include postoperative hypocalcemia or hypoparathyroidism, recurrent laryngeal nerve (RLN) injury, external branch of superior laryngeal nerve injury where documented, hemorrhage or neck hematoma, wound infection, seroma, chyle leak, dysphagia, and death.
Complication risk may vary according to patient factors such as age, sex, comorbidities, diagnosis, thyroid gland size, and preoperative biochemical status. Operative factors, including surgical extent, reoperation, central/lateral neck dissection, emergency surgery, operative duration, surgeon experience or case volume, and pathology, may also contribute.
A local retrospective cohort study will quantify the frequency and timing of post-thyroidectomy complications and identify factors independently associated with these outcomes. Findings can guide preoperative counselling, risk stratification, postoperative monitoring, and quality-improvement measures.
2. Research question
Among patients undergoing thyroidectomy at [Hospital Name], what are the frequency, types, and timing of post-thyroidectomy complications, and which patient-, disease-, and procedure-related factors are associated with their occurrence?
3. Objectives
3.1 Primary objective
To determine the proportion of patients who develop any post-thyroidectomy complication within 30 days after surgery.
3.2 Secondary objectives
- To estimate the incidence of individual complications:
- Hypocalcemia
- Transient and permanent hypoparathyroidism
- Temporary and permanent RLN palsy
- Postoperative hemorrhage or neck hematoma
- Surgical-site infection
- Seroma
- Chyle leak
- Reoperation
- Readmission within 30 days
- Mortality within 30 days
- To describe the severity, management, and timing of complications.
- To identify factors associated with:
- Any postoperative complication
- Postoperative hypocalcemia or hypoparathyroidism
- RLN palsy
- Postoperative hematoma requiring intervention
- To compare complication rates by extent of surgery, especially total/completion thyroidectomy versus hemithyroidectomy.
4. Hypotheses
- Total or completion thyroidectomy is associated with a higher likelihood of postoperative hypocalcemia than hemithyroidectomy.
- Central neck dissection, reoperative surgery, thyroid malignancy, hyperthyroidism/Graves disease, and longer operative duration are associated with a higher risk of postoperative complications.
- Lower surgeon case volume or less surgical experience, if measurable, is associated with a higher risk of complications.
5. Study design
A single-center retrospective cohort study using routinely collected clinical, operative, laboratory, pathology, anesthesia, and follow-up records.
The protocol and eventual report will follow the STROBE guidance for observational studies and the RECORD statement if routinely collected electronic health-record data are used.
6. Study setting
The study will be conducted at [Hospital Name], a [tertiary/referral/general] hospital in [location].
Study period: All eligible thyroidectomy procedures performed from [1 January 2021] to [31 December 2025].
Follow-up period: From the operation date through discharge and up to 30 postoperative days. For classification of permanent hypoparathyroidism or nerve injury, records up to 12 months postoperatively will be reviewed where available.
7. Study population
7.1 Source population
All patients undergoing thyroid surgery at [Hospital Name] during the study period.
7.2 Inclusion criteria
Include patients who:
- Underwent hemithyroidectomy/lobectomy, subtotal thyroidectomy, near-total thyroidectomy, total thyroidectomy, completion thyroidectomy, or thyroidectomy with neck dissection.
- Had surgery during the defined study period.
- Have an operative report and at least one postoperative clinical record, laboratory result, or follow-up note.
7.3 Exclusion criteria
Exclude:
- Procedures limited to biopsy, drainage, or non-thyroid neck surgery.
- Parathyroid surgery without thyroidectomy.
- Patients with missing operative details preventing confirmation of the thyroid procedure.
- Patients with documented preoperative permanent hypoparathyroidism, for analyses of new postoperative hypoparathyroidism.
- Patients with documented preoperative vocal cord palsy, for analyses of new RLN palsy.
- Duplicate records for the same operation. If a patient undergoes more than one eligible operation, each operation may be treated as an episode, but repeat procedures should be flagged and accounted for in analysis.
8. Sample size
A consecutive sample of all eligible procedures during the study period will be used.
For multivariable logistic regression, the number of predictor variables will be limited according to the number of outcome events. As a pragmatic rule, aim for at least 10 to 20 outcome events per model parameter. If the rate of “any complication” is low, the number of covariates will be reduced, clinically related variables will be combined, or penalized regression will be considered.
9. Study variables
9.1 Outcomes
Primary outcome
Any post-thyroidectomy complication within 30 days, defined as the occurrence of one or more prespecified complications below.
Secondary outcomes and operational definitions
| Outcome | Proposed operational definition |
|---|---|
| Postoperative hypocalcemia | Total serum calcium below the hospital laboratory lower limit of normal, albumin-corrected calcium below normal, ionized calcium below normal, or documented symptoms requiring calcium treatment within 30 days. Record the exact laboratory threshold used. |
| Symptomatic hypocalcemia | Perioral tingling, paresthesia, muscle cramps, tetany, carpopedal spasm, seizure, or ECG changes attributed to hypocalcemia, with or without biochemical confirmation. |
| Transient hypoparathyroidism | Low or inappropriately normal postoperative PTH with hypocalcemia requiring calcium and/or calcitriol treatment, resolving within 6 months. |
| Permanent hypoparathyroidism | Requirement for calcium and/or active vitamin D treatment, or persistent biochemical hypoparathyroidism, beyond 12 months after surgery. A 12-month definition should be prespecified and applied consistently. |
| Temporary RLN palsy | New postoperative vocal-cord mobility impairment documented by laryngoscopy, resolving within 12 months. |
| Permanent RLN palsy | New vocal-cord mobility impairment persisting at or beyond 12 months postoperatively. |
| Postoperative neck hematoma/hemorrhage | Clinically diagnosed neck swelling or bleeding after surgery, especially if causing airway concern, requiring aspiration, wound opening, blood transfusion, return to theatre, or prolonged admission. |
| Seroma | Clinically detected postoperative fluid collection requiring observation, aspiration, drainage, or intervention. |
| Surgical-site infection | Infection of the incision or operative site diagnosed clinically and/or treated with antibiotics, drainage, or reoperation within 30 days. |
| Chyle leak | Milky drain output or fluid collection confirmed clinically or biochemically after neck dissection. |
| Reoperation | Unplanned return to the operating theatre related to a postoperative complication. |
| Readmission | Unplanned hospital readmission related to the thyroidectomy within 30 days. |
| Mortality | Death from any cause within 30 days of surgery or during the index admission. |
Important: Record whether laryngoscopy was performed preoperatively and postoperatively. If laryngoscopy was not universal, reported RLN-palsy rates should be described as clinically detected/documented rates, with this limitation clearly acknowledged.
9.2 Exposure and potential associated factors
A. Patient-related factors
- Age at surgery, years
- Sex
- Body mass index, kg/m², if available
- Residence or referral status, if relevant
- Smoking status
- American Society of Anesthesiologists classification
- Comorbidities:
- Hypertension
- Diabetes mellitus
- Chronic kidney disease
- Cardiovascular disease
- Chronic pulmonary disease
- Coagulopathy
- Anticoagulant or antiplatelet use
- Preoperative calcium, albumin, PTH, vitamin D, and thyroid-function tests, if available
- Previous neck irradiation
- Previous thyroid or neck surgery
B. Disease-related factors
- Primary indication for surgery:
- Benign multinodular goiter
- Solitary nodule
- Toxic multinodular goiter
- Graves disease
- Suspicion of malignancy
- Confirmed thyroid cancer
- Compressive symptoms
- Other
- Preoperative thyroid functional state:
- Euthyroid
- Hyperthyroid
- Hypothyroid
- Goiter size or thyroid volume, if available
- Retrosternal extension
- Cytology category
- Final histopathology
- Presence of thyroiditis, including Hashimoto thyroiditis
- Lymph-node metastasis, if cancer is present
C. Procedure-related factors
- Type and extent of operation:
- Hemithyroidectomy/lobectomy
- Subtotal thyroidectomy
- Near-total thyroidectomy
- Total thyroidectomy
- Completion thyroidectomy
- Central neck dissection
- Lateral neck dissection
- Primary versus reoperative surgery
- Elective versus emergency surgery
- Operative duration, minutes
- Estimated blood loss, mL
- Use of drain
- Intraoperative nerve monitoring, if used
- Identification/preservation of parathyroid glands, if documented
- Parathyroid autotransplantation, if performed
- Accidental parathyroid excision on pathology
- Surgeon identity, grade, specialty, years of experience, or annual thyroidectomy volume where data permit
- Year of surgery, to account for changes in practice over time
10. Data sources and collection procedure
10.1 Data sources
Data will be extracted from:
- Operating-theatre register
- Electronic medical records
- Surgical admission and discharge records
- Operative notes
- Anesthesia records
- Laboratory database
- Radiology records
- Histopathology reports
- Outpatient clinic notes
- Laryngoscopy reports
- Emergency department and readmission records
10.2 Case identification
Eligible patients will be identified using procedure codes, theatre registers, and surgical logbooks. The case list will be cross-checked against pathology records where feasible to reduce missed cases.
10.3 Data-collection instrument
A standardized, pilot-tested case-report form or password-protected electronic database will be created. Each participant will receive a unique study identification number. Direct identifiers will be removed from the analytic dataset.
10.4 Data-quality assurance
- Train abstractors using a written data dictionary.
- Pilot the form on 10 to 20 records and refine definitions before full extraction.
- Double-enter or independently audit at least 10% of records.
- Resolve discrepancies by review of the original clinical record and discussion with the principal investigator.
- Document missing values separately rather than inferring absent data as normal.
11. Statistical analysis plan
11.1 General approach
Data analysis will be performed using [R/Stata/SPSS] version [X]. Statistical significance will be set at a two-sided p < 0.05, with 95% confidence intervals.
11.2 Descriptive analysis
- Summarize continuous data as mean ± standard deviation if approximately normally distributed, or median with interquartile range if skewed.
- Summarize categorical data as frequency and percentage.
- Calculate the incidence of each complication and any complication with 95% confidence intervals.
- Describe the timing of complications: immediate, before discharge, and after discharge/readmission.
11.3 Bivariable analysis
Compare patients with and without the primary outcome:
- Categorical variables: chi-square test or Fisher exact test.
- Continuous variables: independent-samples t-test or Mann-Whitney U test.
- For comparisons by procedure type, use chi-square/Fisher exact tests and ANOVA/Kruskal-Wallis testing as appropriate.
11.4 Multivariable analysis
Perform multivariable logistic regression for:
- Any postoperative complication within 30 days
- Postoperative hypocalcemia/hypoparathyroidism, if the number of events allows
- RLN palsy, if the number of events allows
- Postoperative hematoma requiring intervention, only if sufficient events occur
Candidate variables should be chosen based on clinical relevance, published evidence, and bivariable results. A prespecified core model may include:
- Age
- Sex
- Comorbidity burden or ASA class
- Indication/pathology
- Extent of thyroidectomy
- Neck dissection
- Reoperative surgery
- Hyperthyroidism/Graves disease
- Operative duration
- Surgeon volume or experience, if available
Report adjusted odds ratios, 95% confidence intervals, and p-values. Assess collinearity before modeling. For sparse outcomes, use penalized logistic regression or report descriptive/bivariable findings rather than unreliable multivariable estimates.
11.5 Missing data
- Report missingness for every key variable.
- Use complete-case analysis if missing data are minimal and plausibly random.
- If clinically important covariates have substantial missingness, consider multiple imputation if assumptions and sample size permit.
- Do not classify undocumented complications as absent without confirming that follow-up was adequate.
11.6 Sensitivity analyses
Where data permit:
- Restrict analysis to patients with documented 30-day follow-up.
- Restrict RLN-palsy analysis to patients with postoperative laryngoscopy.
- Compare total/completion thyroidectomy against hemithyroidectomy.
- Reclassify hypocalcemia using biochemical criteria only versus biochemical or treatment-based criteria.
- Exclude patients undergoing concomitant central/lateral neck dissection to assess the effect of thyroidectomy alone.
12. Bias and methods to reduce it
| Potential bias | Mitigation |
|---|---|
| Selection bias | Include consecutive eligible patients across a clearly defined period; use theatre, surgical, and pathology registers for case ascertainment. |
| Information bias | Use prespecified outcome definitions; train data abstractors; audit extracted records. |
| Detection bias | Record whether postoperative calcium testing and laryngoscopy were performed; conduct sensitivity analyses among tested patients. |
| Confounding | Use clinically informed multivariable regression and stratified/sensitivity analyses. |
| Loss to follow-up | Report the proportion with 30-day and 12-month follow-up; avoid assuming an absent complication when follow-up is unavailable. |
| Misclassification of permanent outcomes | Use a consistent 12-month definition and confirm status through follow-up, medication records, laboratory data, and specialty notes. |
13. Ethical considerations
- Obtain approval from the [Institutional Review Board/Ethics Committee] before data extraction.
- Request a waiver of informed consent because this is a minimal-risk retrospective chart review, where permitted by local regulations.
- Maintain confidentiality through coded study identifiers and storage of the linkage file separately from the analytic dataset.
- Store electronic data on an encrypted, password-protected institutional device or server.
- Limit access to authorized study staff only.
- Present aggregate results only, without patient-identifying information.
14. Dissemination plan
Findings will be presented to the Department of Surgery/ENT and hospital quality-improvement committee, submitted to a peer-reviewed journal, and presented at relevant scientific meetings. Results may guide standardized postoperative calcium monitoring, laryngoscopy pathways, discharge criteria, and referral or supervision policies for complex thyroid surgery.
15. Proposed timeline
| Activity | Estimated duration |
|---|---|
| Ethics approval | 1-2 months |
| Develop database and pilot data form | 2-3 weeks |
| Case identification and data extraction | 2-4 months |
| Data cleaning and quality audit | 2-4 weeks |
| Statistical analysis | 3-4 weeks |
| Manuscript preparation | 4-6 weeks |
16. Suggested abstract for the protocol
Background: Thyroidectomy is associated with complications including hypocalcemia/hypoparathyroidism, recurrent laryngeal nerve palsy, cervical hematoma, wound complications, and readmission. Local complication rates and determinants may differ according to case mix, surgical expertise, and perioperative care pathways.
Methods: This single-center retrospective cohort study will include consecutive patients undergoing thyroidectomy at [Hospital Name] between [start date] and [end date]. Data will be collected from operative, anesthesia, laboratory, pathology, and follow-up records. The primary outcome is any post-thyroidectomy complication within 30 days. Secondary outcomes include hypocalcemia/hypoparathyroidism, RLN palsy, hematoma, wound complications, reoperation, readmission, and mortality. Patient-, disease-, and procedure-related factors will be examined using descriptive statistics, bivariable tests, and multivariable logistic regression.
Ethics and dissemination: Institutional ethics approval will be obtained. De-identified data will be securely managed. Results will be disseminated through institutional presentation and peer-reviewed publication.
17. Recent-evidence note
Recent systematic reviews have examined risk factors for transient and permanent hypoparathyroidism after thyroidectomy, including a 2024 meta-analysis (PMID: 38652139) and a newer 2026 review (PMID: 41217744). These support treating postoperative calcium/parathyroid outcomes as major prespecified endpoints and carefully recording operative extent, pathology, and perioperative biochemical testing.
Quick answer
Retrospective Study Protocol
Title
Post-thyroidectomy complications and associated factors among patients undergoing thyroid surgery at [Hospital Name], [City/Country]: a retrospective cohort study
1. Background and rationale
Thyroidectomy is a commonly performed operation for benign and malignant thyroid disease. Although generally safe, it can cause clinically important complications, particularly postoperative hypocalcemia or hypoparathyroidism, recurrent laryngeal nerve injury with vocal-cord dysfunction, postoperative cervical hematoma, surgical-site infection, seroma, and rarely airway compromise or death.
Patients undergoing total or completion thyroidectomy require monitoring for hypocalcemia, bleeding, and recurrent laryngeal nerve injury. The frequency and predictors of these complications vary by patient factors, thyroid pathology, surgical extent, urgency, reoperation status, lymph-node dissection, and surgeon or hospital factors. Local data are necessary to quantify the burden of complications and identify modifiable risk factors that can improve perioperative care and surgical outcomes.
This protocol follows the principles of STROBE and, where routinely collected health-record data are used, the RECORD reporting recommendations.
2. Research question
Among patients who undergo thyroidectomy at [Hospital Name], what is the incidence of post-thyroidectomy complications, and which patient, disease-related, and operative factors are associated with their occurrence?
3. Objectives
3.1 Primary objective
To determine the proportion of patients who develop one or more complications after thyroidectomy.
3.2 Secondary objectives
-
To determine the incidence of individual post-thyroidectomy complications, including:
- Hypocalcemia and hypoparathyroidism
- Recurrent laryngeal nerve palsy or postoperative voice change
- Postoperative neck hematoma or bleeding
- Seroma
- Surgical-site infection
- Wound dehiscence
- Airway compromise, tracheostomy, or reintubation
- Readmission, reoperation, prolonged hospital stay, and mortality
-
To describe the timing, severity, management, and outcomes of complications.
-
To identify factors associated with any post-thyroidectomy complication.
-
To identify factors specifically associated with postoperative hypocalcemia and recurrent laryngeal nerve injury, if sufficient outcome events are available.
4. Hypotheses
- Complications are more frequent after total or completion thyroidectomy than after lobectomy or subtotal thyroidectomy.
- Malignancy, Graves disease/toxic goiter, large or retrosternal goiter, thyroiditis, reoperative surgery, central/lateral neck dissection, and longer operative duration are associated with higher odds of complications.
- Older age, relevant comorbidity, emergency surgery, and lower surgeon procedural volume may also be associated with adverse postoperative outcomes.
5. Methods
5.1 Study design
A retrospective cohort study based on review of medical records, operative registers, anesthesia records, laboratory records, pathology reports, and follow-up clinic documentation.
5.2 Study setting
The study will be conducted at [Hospital Name], a [primary/secondary/tertiary] hospital in [City, Country]. The hospital provides thyroid surgery and postoperative follow-up through the departments of [General Surgery/Otolaryngology/Endocrine Surgery].
5.3 Study period
Records of eligible patients operated between [start date] and [end date] will be reviewed.
A period of at least 2 to 5 years is suggested to ensure an adequate sample and enough complication events for multivariable analysis.
5.4 Population
All eligible patients undergoing thyroidectomy during the study period will be included consecutively.
5.5 Eligibility criteria
Inclusion criteria
- Patients of any age undergoing thyroid surgery at the study hospital during the defined period.
- Procedures including:
- Total thyroidectomy
- Near-total thyroidectomy
- Subtotal thyroidectomy
- Hemithyroidectomy or thyroid lobectomy
- Completion thyroidectomy
- Medical records containing at minimum:
- Type of thyroid operation
- Immediate postoperative outcome or discharge documentation
Exclusion criteria
- Patients undergoing procedures limited to thyroid biopsy, drainage, or isolated non-thyroid neck surgery.
- Records with no operative report or no postoperative outcome documentation.
- Patients whose surgery was performed elsewhere and who only presented for follow-up, unless the study specifically includes referred postoperative complications.
- Duplicate records of the same operation.
Handling of incomplete data: Records with missing covariates should not automatically be excluded. The extent and pattern of missingness will be reported. Patients with missing primary-outcome information will be excluded from analysis of that outcome.
6. Variables and operational definitions
6.1 Outcome variable
Primary outcome: any post-thyroidectomy complication
Defined as the occurrence of at least one documented surgical, biochemical, or clinical complication from the end of surgery until discharge, or within 30 days postoperatively. A longer follow-up period may be used for persistent complications.
Individual complications
| Complication | Proposed operational definition |
|---|---|
| Postoperative hypocalcemia | Serum corrected calcium below the institutional lower reference limit after surgery, and/or symptoms requiring calcium treatment. The exact laboratory cut-off should be stated, for example corrected calcium <2.0 mmol/L or total calcium <8.0 mg/dL. |
| Transient hypoparathyroidism/hypocalcemia | Hypocalcemia or need for calcium with or without calcitriol resolving within 6 months after surgery. |
| Permanent hypoparathyroidism | Persistent hypocalcemia or continued requirement for calcium and/or active vitamin D beyond 6 months after surgery. If local practice uses 12 months, this must be stated and applied consistently. |
| Recurrent laryngeal nerve injury | New postoperative vocal-cord paresis/paralysis confirmed by laryngoscopy, or documented postoperative hoarseness consistent with nerve injury where laryngoscopy is unavailable. |
| Transient recurrent laryngeal nerve palsy | Recovery of vocal-cord movement or voice within 6 months. |
| Permanent recurrent laryngeal nerve palsy | Persistent documented palsy at 6 months or later. |
| Neck hematoma/bleeding | Clinically apparent postoperative neck collection or bleeding diagnosed by examination, imaging, aspiration, or reoperation. |
| Severe hematoma | Hematoma causing respiratory compromise, requiring urgent wound opening, evacuation in theatre, blood transfusion, reintubation, or tracheostomy. |
| Seroma | Postoperative fluid collection requiring observation, aspiration, or drainage. |
| Surgical-site infection | Purulent wound discharge, cellulitis, abscess, or infection documented by the treating clinician within 30 days. |
| Airway complication | Stridor, respiratory distress, reintubation, emergency tracheostomy, or intensive-care admission due to a thyroidectomy-related airway event. |
| Reoperation | Return to theatre for bleeding, hematoma, wound complication, residual disease, or another thyroidectomy-related indication during index admission or within 30 days. |
| Prolonged hospital stay | Length of stay greater than the study hospital's usual postoperative stay for uncomplicated thyroidectomy, preferably defined before data collection. |
| Mortality | Death during the index admission or within 30 days of surgery. |
6.2 Exposure variables and potential associated factors
Sociodemographic factors
- Age at surgery, in years
- Sex
- Residence, if documented
- Health insurance/payment status, if relevant to local care access
Clinical factors
- Body mass index, if available
- American Society of Anesthesiologists classification
- Comorbidities:
- Hypertension
- Diabetes mellitus
- Chronic kidney disease
- Cardiovascular disease
- Coagulopathy
- Chronic anticoagulant or antiplatelet use
- Smoking status, if documented
- Preoperative thyroid function status: euthyroid, hyperthyroid, hypothyroid
- Preoperative serum calcium, albumin, vitamin D, parathyroid hormone, and hemoglobin, where available
- Indication for surgery:
- Suspected or confirmed malignancy
- Benign multinodular goiter
- Solitary thyroid nodule
- Graves disease
- Toxic multinodular goiter
- Compressive symptoms
- Recurrent goiter
- Indeterminate cytology
- Preoperative diagnosis and fine-needle aspiration result
- Thyroid size, nodule size, retrosternal extension, compressive symptoms, and radiologic findings
Operative and pathology factors
- Type of procedure: lobectomy, subtotal, near-total, total, or completion thyroidectomy
- Elective versus emergency operation
- Primary versus reoperative thyroid surgery
- Central and/or lateral neck dissection
- Intraoperative identification or autotransplantation of parathyroid glands, if documented
- Use of intraoperative nerve monitoring, if available
- Operative duration
- Estimated blood loss
- Drain insertion
- Surgeon specialty and experience level
- Surgeon case volume, if feasible
- Histopathology:
- Benign disease
- Thyroiditis
- Differentiated thyroid carcinoma
- Other malignancy
- Tumor stage or nodal disease for malignant cases, if available
7. Sample size and sampling method
All eligible records during the study period will be included using consecutive sampling.
For the multivariable logistic regression model, the number of predictor variables will be limited according to the number of observed events. As a practical minimum, aim for at least 10 outcome events per parameter included in the final model. If complications are uncommon, the analysis will use fewer predictors, combine clinically similar categories, or focus on the most frequent complication, commonly postoperative hypocalcemia.
8. Data sources and data collection procedure
- Identify all thyroidectomy cases from theatre logs, surgical registries, discharge databases, and pathology records.
- Screen records against eligibility criteria.
- Assign each eligible patient a unique study identification number.
- Extract data using a pretested standardized data-collection form.
- Cross-check complications using:
- Operative notes
- Postoperative progress notes
- Medication charts
- Serum calcium and parathyroid hormone results
- Laryngoscopy records
- Readmission and reoperation records
- Outpatient follow-up documentation
- Record no direct patient identifiers in the analytic dataset.
A pilot review of approximately 5% to 10% of records should be conducted to test clarity and completeness of the data tool. If possible, a second reviewer should independently check a random subset of records to assess data-extraction consistency.
9. Data quality assurance
- Train data collectors using a written study manual with explicit definitions.
- Pretest the extraction form before full data collection.
- Use predefined coding categories and a data dictionary.
- Double-enter data or conduct double-checking of a random sample.
- Reconcile discrepancies by re-reviewing the source record.
- Perform range checks and logical checks, for example:
- Completion thyroidectomy cannot be coded as a first operation.
- Permanent complications require adequate follow-up.
- A total thyroidectomy should not be coded with only one lobe removed.
- Maintain a secure linkage file separately from the research dataset, if linkage is necessary.
10. Statistical analysis plan
10.1 Data preparation
Data will be entered into [REDCap/EpiData/Excel] and analyzed using [SPSS/Stata/R].
- Continuous variables will be assessed for distributional characteristics.
- Normally distributed data will be summarized as mean ± standard deviation.
- Skewed data will be summarized as median with interquartile range.
- Categorical variables will be presented as frequencies and percentages.
- Missing data will be described for every key variable.
10.2 Descriptive analysis
- Calculate the incidence of any complication and each individual complication.
- Report complications overall and stratified by type of thyroid operation.
- Describe indications, operative characteristics, management, length of stay, reoperation, readmission, and mortality.
10.3 Bivariable analysis
Patients with and without any postoperative complication will be compared using:
- Chi-square test or Fisher's exact test for categorical variables.
- Independent-samples t-test for normally distributed continuous variables.
- Mann-Whitney U test for non-normally distributed continuous variables.
Crude odds ratios with 95% confidence intervals will be calculated.
10.4 Multivariable analysis
Binary logistic regression will identify independent factors associated with:
- Any post-thyroidectomy complication.
- Postoperative hypocalcemia, if the event count permits.
- Recurrent laryngeal nerve injury, if the event count permits.
Variables selected a priori for clinical relevance, along with variables with bivariable p <0.20, will be considered for the multivariable model. Likely core variables include age, sex, comorbidity burden, indication for surgery, thyroid malignancy, type of thyroidectomy, reoperation status, neck dissection, operative duration, and surgeon experience/volume.
Adjusted odds ratios with 95% confidence intervals and p-values will be reported. Statistical significance will be set at p <0.05.
10.5 Model diagnostics
- Assess multicollinearity using variance inflation factors.
- Examine model fit using an appropriate goodness-of-fit test.
- Check for clinically plausible interactions, particularly:
- Extent of thyroidectomy × neck dissection
- Malignancy × neck dissection
- Reoperation × operative duration
- Conduct sensitivity analyses, where feasible, such as restricting the primary outcome to complications objectively confirmed by laboratory testing, laryngoscopy, imaging, or reoperation.
11. Ethical considerations
Ethical approval will be sought from the [Name of Institutional Review Board/Ethics Committee] before study commencement.
Because this is a retrospective record review involving no direct patient contact and no alteration of care, a waiver of informed consent will be requested where permitted by local regulations. Patient confidentiality will be protected by using coded study identifiers, removing names and medical-record numbers from the analysis dataset, limiting access to authorized investigators, and storing electronic data in password-protected files.
12. Risks and benefits
There is minimal risk to participants because the study uses existing medical records. The principal risk is potential breach of confidentiality, mitigated through de-identification and secure data handling.
Potential benefits include identification of preventable perioperative risk factors, improved patient counselling, enhanced postoperative monitoring, and targeted quality-improvement interventions.
13. Expected limitations
- Retrospective records may have missing or inaccurately documented variables.
- Patients without documented laryngoscopy may have underdiagnosed recurrent laryngeal nerve injury.
- Follow-up may be insufficient to distinguish transient from permanent hypoparathyroidism or nerve palsy.
- Surgeon experience, parathyroid identification, blood loss, and operative complexity may be incompletely recorded.
- Associations identified cannot prove causality.
- A single-center study may have limited generalizability.
14. Dissemination plan
Findings will be presented to the Departments of [Surgery/Otolaryngology/Endocrinology], submitted to an institutional research forum, and prepared for publication in a peer-reviewed surgical or endocrine journal. Results will be reported using STROBE and RECORD principles.
15. Proposed timeline
| Activity | Estimated duration |
|---|---|
| Ethics approval | 1-2 months |
| Development and piloting of data tool | 2 weeks |
| Case identification and record review | 1-3 months |
| Data cleaning and analysis | 2-4 weeks |
| Report/manuscript preparation | 1 month |
16. Suggested data-collection fields
Patient details: study ID, age, sex, date of surgery, comorbidities, ASA class, thyroid function, preoperative calcium/albumin/PTH.
Disease characteristics: indication, goiter/nodule size, retrosternal extension, cytology, malignancy suspicion, thyroiditis, Graves disease, pathology result.
Operation details: procedure type, elective/emergency status, primary/reoperative surgery, neck dissection, operative duration, blood loss, drain use, surgeon level/volume, nerve monitoring, parathyroid autotransplantation.
Outcomes: postoperative calcium, symptoms of hypocalcemia, calcium/calcitriol treatment, laryngoscopy result, voice change, hematoma, reoperation, wound infection, seroma, airway event, length of stay, readmission, mortality, status at 6 months.
Key evidence basis: Thyroidectomy complications of particular interest include hypoparathyroidism or hypocalcemia, recurrent laryngeal nerve injury, and postoperative neck hematoma. Recent systematic reviews also support focused assessment of risk factors for transient and permanent postoperative hypoparathyroidism, including the 2024 review indexed as PMID 38652139 and the 2026 review indexed as PMID 41217744.
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