First-line thyroid function tests -- TSH alone is not enough

Frequency, determinants and costs of thyroid function testing in a laboratory serving a large population

OBJECTIVE

To assess the rationale and frequency of thyroid function testing and to analyse factors that influence serum thyrotropin (TSH) levels.

PATIENTS, DESIGN AND MAIN OUTCOME MEASURES

Serum TSH levels were evaluated in a hospital laboratory serving a population of 604 000 in 2018. Patients on medications or with conditions affecting thyroid function were excluded. Frequency of thyroid function testing by age and sex was assessed and the relationship between serum TSH with potential predictor variables was analysed using ordinary least square regression analysis allowing for potential non-linearity.

RESULTS

Twenty-eight percent of the local population had their thyroid function tested at least once in 2018 with significant differences by sex (28.2% women vs 23.4% men) and by age groups, with less than 2% of <16-year-old people and more than 50% of >80-year-old people being tested. Most of the symptoms commonly attributed to thyroid dysfunction were not higher in the thyroid dysfunction groups. Serum TSH levels were higher in older people particularly after the age of 60 years, in women (by 0.1 mIU/L), during the early hours of the morning, and in winter and spring seasons. There was remarkable uniformity in the frequency of subclinical thyroid dysfunction, as well as substantial cost savings, if TSH reference intervals were recalculated across sexes, age groups, time-periods and seasons.

CONCLUSIONS

Serum TSH is frequently tested in the population but is not a good discriminant of symptoms attributed to thyroid dysfunction. Furthermore, considering the influence of factors on TSH reference limits could significantly impact patient care and resource utilisation.

Frequency of thyroid function tests and examinations in participants of a population-based study

BACKGROUND

Thyroid disorders are common in the adult German population. Little is known about guideline implementation in clinical practice and the prevalence of diagnostic procedures in ambulatory care. The study aims to investigate the use of thyroid hormone measurements, thyroid ultrasound, thyroid scintiscan and associated costs in ambulatory care at population level.

METHODS

Data were derived from two independent population-based cohorts of the Study of Health In Pomerania (SHIP). Ambulatory billing data from the Association of Statutory Health Insurance Physicians Mecklenburg-Vorpommern were individually linked for the period 2002-2016 with SHIP data. The main outcomes were the frequency of outpatient ultrasound, scintiscan, serum TSH level measurement, free triiodothyronine (fT3) and free thyroxine (fT4) measurement, TSH-receptor-antibodies and microsomal antibodies measurement within 1 year and 3 years prior to the study entrance of the participants. Multinomial logistic regression models were used to assess the association of age, sex, thyroid medication intake and Charlson-Comorbidity-Index with frequency of TSH measurements and ultrasound examinations.

RESULTS

A total of 5552 participants (47% male, median age 55) were included in the analysis. 25% (1409/5552) had a diagnosed thyroid disorder or treatment, 40% (2191/5552) had clinical findings based on ultrasound or laboratory testing in SHIP only and 35% (1952/5552) neither a coded thyroid disorder or clinical finding nor thyroid medication. In the total study population 30% (1626/5552) received at least one TSH measurement, 6.8% (378/5552) at least one thyroid ultrasound and 2.6% (146/5552) at least one scintiscan within the past year before the study examination. Tests were performed more frequently in patients with thyroid medication and coded thyroid disorders. Hence, this group caused the highest expenditures.

CONCLUSIONS

Given the high prevalence of thyroid disorders, diagnostic and monitoring tests should be used rationally with regard to costs. TSH levels should be monitored regularly in patients on thyroid medication. A consensus on monitoring frequency and iteration of monitoring of morphological thyroid disorders with TSH and ultrasound and specific guideline recommendations are needed.

TRIAL REGISTRATION

Versorgungsforschung Deutschland (VfD_17_003880).

Subclinical thyroid dysfunction symptoms in older adults: cross-sectional study in UK primary care

BACKGROUND

Subclinical thyroid dysfunction - abnormal serum thyrotrophin (thyroid-stimulating hormone; TSH) concentrations with normal free thyroxine (FT4) is common in older people. It remains unclear whether individuals with subclinical serum status experience an increased symptom profile.

AIM

To compare the prevalence of those symptoms typically associated with overt thyroid dysfunction in older individuals with a subclinical and euthyroid serum profile.

DESIGN AND SETTING

Cross-sectional study, nested within the Birmingham Elderly Thyroid Study (BETS); from 19 UK general practices.

METHOD

Adults living in a community setting (aged ≥65 years), without overt thyroid dysfunction or associated treatment, self-reported the presence or absence of 18 symptoms (while serum result naïve). Serum concentrations of TSH and FT4 were measured to establish thyroid status.

RESULTS

A total of 2870 individuals were screened: 2703 (94%) were categorised as euthyroid (normal), 29 (1%) subclinically hyperthyroid, and 138 (5%) subclinically hypothyroid. Symptoms were common in all groups. No significant differences in the prevalence of individual symptoms were observed between the euthyroid and subclinically hypothyroid groups nor in comparison with the subclinically hyperthyroid group. Multivariate logistic regression analysis failed to reveal an association between individual or multiple symptoms and subclinical status.

CONCLUSION

Findings suggest that subclinical thyroid dysfunction does not confer a symptom burden in older individuals and support adherence to guidelines in the non-treatment of subclinical thyroid dysfunction. GPs may use the findings to reassure older people presenting with symptoms that subclinical thyroid dysfunction is an unlikely explanation. The presence of persistently abnormal TSH concentrations may be linked to long-term risks of cardiovascular disease, especially atrial fibrillation, but whether this should prompt treatment and whether such treatment alters vascular outcomes is unknown.

Interference in thyroid function immunoassays: clinical consequences

Thyroid function tests are prone to analytical interference, which can cause misleading results when performed on automated immunoassay analyzers. We present a case of a 68-years old woman diagnosed with primary hypothyroidism and chronically treated with levothyroxine. Her status has been followed-up in several different institutions and before readmission to our institute, she was diagnosed as T3 toxicosis according to the lab results of suppressed TSH, normal FT4 and highly elevated FT3 values. Due to lack of toxic symptoms, our clinician suspected FT3 test interference, which was confirmed in our lab by performing the test on a different immunoassay platform. In conclusion, every discrepancy between clinical presentation and laboratory test results has to be inspected by close communication between clinicians and laboratory specialists. Our goal was to raise the awareness within the healthcare community about the interference in immunoassays affecting different kit manufacturers and analytical platforms in order to avoid erroneous diagnosis and mistreatment of patients. Key words: immunoassay, interference, free triiodothyronine, mistreatment

Primary care use of laboratory tests in Northern Ireland's Western Health and Social Care Trust: a cross-sectional study

OBJECTIVES

To describe the laboratory test ordering patterns by general practitioners (GPs) in Northern Ireland Western Health and Social Care Trust (WHSCT) and explore demographic and socioeconomic associations with test requesting.

DESIGN

Cross-sectional study.

SETTING

WHSCT, Northern Ireland. : Particip ANTS: 55 WHSCT primary care medical practices that remained open throughout the study period 1 April 2011-31 March 2016.

OUTCOMES

To identify the temporal patterns of laboratory test ordering behaviour for eight commonly requested clinical biochemistry tests/test groups in WHSCT. To analyse the extent of variations in laboratory test requests by GPs and to explore whether these variations can be accounted for by clinical outcomes or geographical, demographic and socioeconomic characteristics.

RESULTS

The median number of adjusted test request rates over 5 consecutive years of the study period decreased by 45.7% for urine albumin/creatinine ratio (p<0.000001) and 19.4% for lipid profiles (p<0.000001) while a 60.6%, 36.6% and 29.5% increase was observed for HbA_1c (p<0.000001), immunoglobulins (p=0.000007) and prostate-specific antigen (PSA) (p=0.0003), respectively. The between-practice variation in test ordering rates increased by 272% for immunoglobulins (p=0.008) and 500% for HbA_1c (p=0.0001). No statistically significant relationship between ordering activity and either demographic (age and gender) and socioeconomic factors (deprivation) or Quality and Outcome Framework scores was observed. We found the rural-urban differences in between-practice variability in ordering rates for lipid profiles, thyroid profiles, PSA and immunoglobulins to be statistically significant at the Bonferroni-adjusted significance level p<0.01.

CONCLUSIONS

We explored potential factors of the interpractice variability in the use of laboratory tests and found that differences in requesting activity appear unrelated to either demographic and socioeconomic characteristics of GP practices or clinical outcome indicators.

Stability of thyroid function in older adults: the Birmingham Elderly Thyroid Study

BACKGROUND

Thyroid function tests (TFTs) are among the most requested tests internationally. However, testing practice is inconsistent, and potentially suboptimal and overly costly. The natural history of thyroid function remains poorly understood.

AIM

To establish the stability of thyroid function over time, and identify predictors of development of overt thyroid dysfunction.

DESIGN AND SETTING

Longitudinal follow-up in 19 general practices in the UK.

METHOD

A total of 2936 participants from the Birmingham Elderly Thyroid Study (BETS 1) with a baseline TFT result indicating euthyroid or subclinical state were re-tested after approximately 5 years. Change in thyroid-stimulating hormone (TSH), free thyroxine (FT₄), and thyroid status between baseline and follow-up was determined. Predictors of progression to overt dysfunction were modelled.

RESULTS

Participants contributed 12 919 person-years; 17 cases of overt thyroid dysfunction were identified, 13 having been classified at baseline as euthyroid and four as having subclinical thyroid dysfunction. Individuals with subclinical results at baseline were 10- and 16-fold more likely to develop overt hypothyroidism and hyperthyroidism, respectively, compared with euthyroid individuals. TSH and FT₄ demonstrated significant stability over time, with 61% of participants having a repeat TSH concentration within 0.5 mIU/L of their original result. Predictors of overt hypothyroidism included new treatment with amiodarone (odds ratio [OR] 92.1), a new diagnosis of atrial fibrillation (OR 7.4), or renal disease (OR 4.8).

CONCLUSION

High stability of thyroid function demonstrated over the 5-year interval period should discourage repeat testing, especially when a euthyroid result is in the recent clinical record. Reduced repeat TFTs in older individuals is possible without conferring risk, and could result in significant cost savings.

Thyroid testing in acutely ill patients may be an expensive distraction

In health, an efficient negative feedback mechanism maintains serum thyroid hormone concentrations within an exquisitely controlled narrow range. Therefore any change that occurs to thyroid hormones in intrinsic thyroid disease is concordant and easy to interpret. Optimal functioning of the many tissues they influence is thereby facilitated.
The situation in acute illnesses is different. Mechanisms that operate in these circumstances influence the hypothalamic-pituitary-thyroid axis and its components producing thyroid test results, which are discordant, do not fit recognizable patterns and are difficult to interpret. The yield of abnormalities is also low (about 7%). As many studies indicate, thyroid tests are expensive and consume large amounts of the hospital budget and resources of hospital laboratories. Other studies have shown that when abnormalities are detected, clinicians do not intervene or follow up these subjects. Therefore the clinical utility of thyroid testing in acutely ill patients is debatable. Interventions to change requestor behaviour with regard to thyroid testing in acutely ill subjects and the success of some audit and educational interventions are worthy of note.
Thyroid testing in acutely ill patients is often an expensive distraction and is of limited clinical value. Targeted thyroid testing should be offered in this group only to those with: (a) symptoms or signs of thyroid disease e.g. goiter or orbitopathy; (b) risk factors for thyroid disease, previous or family history of thyroid disease;

Central hypothyroidism and its role for cardiovascular risk factors in hypopituitary patients

Hypothyroidism is characterized by hypometabolism, and may be seen as a part of secondary failure due to pituitary insufficiency or tertiary due to hypothalamic disease. Secondary and tertiary failures are also referred to as central hypothyroidism. Whereas overt primary hypothyroidism has a well-known affection on the heart and cardiovascular system, and may result in cardiac failure, cardiovascular affection is less well recognized in central hypothyroidism. Studies on central hypothyroidism and cardiovascular outcome are few and given the rarity of the diseases often small. Further, there are several limitations given vast difficulties in diagnosing the condition correctly biochemically, and difficulties monitoring the treatment because normal thyroid-pituitary feedback interrelationships are disrupted. The present review summarizes available studies of central adult hypothyroidism and its possible influence on the cardiovascular system, describe differences from primary thyroid failure and seek evidence for performing guidelines for clinical management of this particular thyroid and hypothalamo-pituitary disorder.

The non-anticoagulation costs of atrial fibrillation management: findings from an observational study in NHS Primary Care

Background:

Atrial fibrillation (AF) management represents a significant burden on the UK NHS. Understanding this burden will be important in informing future health care planning and policy development.

Aim:

To describe the non-anticoagulation costs associated with AF management in routine UK clinical practice.

Materials, patients and methods:

A retrospective observational study of 825 patients with AF undertaken in eight UK primary care practices. Data collected from routine clinical and prescribing records of all eligible, consenting patients, for a period of up to 3 years. The first 12 weeks following diagnosis was defined as the ‘initiation phase’; the period after week 12 was defined as the ‘maintenance phase’.

Results:

Mean (SD) total cost of AF management was £941 (£1094) per patient in the initiation phase and £426 (£597) per patient-year in the maintenance phase. AF-related inpatient admissions contributed most to total costs; the mean (SD) total cost per patient in the initiation phase was £2285 (£900) for admitted and £278 (£252) for non-admitted patients. Mean maintenance phase costs per year were £1323 (£755) and £168 (£234), respectively, for admitted and non-admitted patients. Significant patient variables contributing to high cost in the initiation phase were hypertension and younger patient age, although only accounting for 6% of cost variability. Significant variables in the maintenance phase (18% of cost variability) were the presence of congestive heart failure, structural heart disease or diabetes and the frequency of day case admissions, ECGs and hospitalisations in the initiation phase.

Conclusions:

Inpatient admissions contributed most to total AF management costs. Given the burden of hospital care, future work should focus on evaluating the appropriateness and reasons for hospitalisation in patients with AF and the factors affecting length of stay, with the aim of identifying opportunities to safely reduce inpatient costs.

A number of significant patient characteristics and initiation phase variables were identified, which accounted for 18% of the variability in total maintenance phase costs. However, none of these could adequately predict high maintenance phase costs.

Thyrotropin isoforms: implications for thyrotropin analysis and clinical practice

Serum thyrotropin (TSH) is considered the single most sensitive and specific measure of thyroid function in the general population owing to its negative logarithmic association with free triiodothyronine and free thyroxine concentrations. It is therefore often the test of choice for screening, diagnosis, and monitoring of primary hypothyroidism. Serum TSH concentrations can be analyzed quantitatively using third-generation immunoassays, whereas its bioactivity can be measured by TSH activity assays in cell culture. Theoretically, if serum TSH concentrations are directly related to TSH activity, the two tests should yield comparable results. However, on occasion, the results are discordant, with serum concentrations being higher than TSH biological activity. This review focuses on the dissociation between the clinical state and serum TSH concentrations and addresses clinically important aspects of TSH analysis.

The Use of TSH in Determining Thyroid Disease: How Does It Impact the Practice of Medicine in Pregnancy?

During the last four decades, there have been considerable advances in the efficacy and precision of serum thyroid function testing. The development of the third generation assays for the measurement of serum thyroid stimulating hormone (TSH, thyrotropin) and the log-linear relationship with free thyroxine (T4) established TSH as the hallmark of thyroid function testing. While it is widely accepted that TSH outside of the normal range is consistent with thyroid dysfunction, a vast multitude of additional factors must be considered before an accurate clinical diagnosis can be made. This is especially important during pregnancy, when the thyroid is under considerable additional pregnancy-related demands requiring significant maternal physiological changes. This paper examines serum TSH measurement in pregnancy and some associated potential confounding factors.

Investigation of thyroid dysfunction is more likely in patients with high psychological morbidity

BACKGROUND

Mild or subclinical hypothyroidism [raised thyroid-stimulating hormone (TSH) but normal free thyroxine (T4)] affects 5-10% of adults. Symptoms are non-specific and TSH levels are needed for diagnosis.

OBJECTIVES

We explore the relationship between thyroid function and psychological distress and investigate the usefulness of an expert-designed Thyroid Symptom Questionnaire (TSQ) in identifying hypothyroidism.

METHODS

DEPTH (DEPression and THyroid) is a cross-sectional study of 325 patients recruited from general practices in Bristol, for whom thyroid function tests were requested by the GP. Subjects completed the TSQ, General Health Questionnaire (GHQ-12) and Patient Health Questionnaire (PHQ) and had blood tests for TSH and free T4.

RESULTS

The mean age was 45.7 years; 252 subjects (78%) were female; median TSH was 1.6. Psychological morbidity in this population is high: 54.2% have a GHQ-12 score >3, indicating psychological distress. We found no relationship between TSH and psychological distress [adjusted odds ratio 1.02 (95% confidence interval 0.91-1.13), P = 0.78]. The prevalence of hypothyroidism was 6.2% (95% confidence interval 3.8-9.5%). We found no evidence of an unadjusted association between TSQ score and subclinical hypothyroidism [adjusted odds ratio of 1.09 (95% confidence interval 0.95-1.24), P = 0.23].

CONCLUSIONS

Those referred for thyroid function tests, although no more likely than others to have hypothyroidism, have high rates of psychological distress. When mild (subclinical) hypothyroidism is detected in patients with psychological distress, it is important that GPs are aware that this is likely to be coincidental rather than causal and offer appropriate treatment.

TSH - Clinical Aspects of its Use in Determining Thyroid Disease in the Elderly. How Does it Impact the Practice of Medicine in Aging?

The last four decades have seen enormous growth in the efficacy of serum thyroid stimulating hormone (thyrotropin, TSH) assay methodology, establishing TSH as the hallmark of thyroid testing. At the center of the considerations is the strong inverse correlation between serum thyrotropin and free thyroxine concentrations. While it is widely accepted that elevated serum TSH concentrations are consistent with thyroid dysfunction, a vast multitude of additional factors must be considered before an accurate clinical diagnosis can be made followed by an appropriate treatment. Epidemiological studies have demonstrated slightly elevated serum TSH concentrations among the elderly population. There is, however, a debate whether these elevated TSH levels reflect an increased prevalence of hypothyroidism among the elderly or a normal aspect of healthy aging. A comprehensive analysis of the many variables associated with this debate and TSH measurement as a diagnostic tool in aging should provide insight into the clinical efforts to diagnose and treat thyroid disease, particularly in the elderly population.

What should be done when thyroid function tests do not make sense?

Interpretation of thyroid function tests (TFTs) is generally straightforward. However, in a minority of contexts the results of thyroid hormone and thyrotropin measurements either conflict with the clinical picture or form an unusual pattern. In many such cases, reassessment of the clinical context provides an explanation for the discrepant TFTs; in other instances, interference in one or other laboratory assays can be shown to account for divergent results; uncommonly, genetic defects in the hypothalamic-pituitary-thyroid axis are associated with anomalous TFTs. Failure to recognize these potential 'pitfalls' can lead to misdiagnosis and inappropriate management. Here, focusing particularly on the combination of hyperthyroxinaemia with nonsuppressed thyrotropin, we show how a structured approach to investigation can help make sense of atypical TFTs.

Thyroid Function Tests

A thyroid panel consisting of thyroid stimulating hormone (TSH) and free thyroxine (fT4) should form the first line of diagnostic tests; tri-iodothyronine (T3) — total or free may be needed occasionally. A TSH assay capable of detecting levels below 0.02mIU/L is required to differentiate the suppressed TSH levels typical in Graves' disease from subnormal levels seen in some geriatric patients, non-thyroidal illness, and patients on medications. Additional tests including thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), and TSH receptor antibody (TRAb) may be ordered to enable differential diagnosis when indicated. Serum thyroglobulin (Tg) may serve as a tumour marker for monitoring patients with differentiated thyroid cancer.

Clinical outcome indicators, disease prevalence and test request variability in primary care

Aim

To describe differences in biochemistry test request rates (adjusted for practice size) between general practices and to investigate whether differences in HbA1c and thyroid function test request rates are related either to the practice prevalence of hypothyroidism and diabetes or to Quality and Outcome Framework (QOF) scores.

Methods

Information on test request rates, prevalence of diabetes and hypothyroidism, and QOF data over a one-year period were obtained from 58 practices covering a population of 284,609 patients. Spearman's rank correlation tests were used to investigate relationships between adjusted test request rates.

Results

There was wide variability in adjusted test request rates (lowest for HbA1c and highest for immunoglobulins). The ranking of practices for different tests was highly correlated. There was no relationship between adjusted test request rates for HbA1c and thyroid function and the reported prevalence of diabetes and hypothyroidism, respectively, nor was there any relationship with QOF scores in diabetes and hypothyroidism.

Conclusions

There is wide variability in test request rates in general practice that do not appear to be related to disease prevalence or crude clinical outcome measures.

Thyroid dysfunction in patients with diabetes: clinical implications and screening strategies

BACKGROUND

Patients with diabetes mellitus are at an increased risk of thyroid disease. The frequency of thyroid dysfunction in diabetic patients is higher than that of the general population and up to a third of patients with type-1 diabetes (T1DM) ultimately develop thyroid dysfunction. Unrecognised thyroid dysfunction may impair metabolic control and add to cardiovascular disease risk in diabetic patients.

AIMS

Our aims were to review the current literature on the association between thyroid dysfunction and diabetes mellitus, to highlight relevant clinical implications, and to examine present thyroid disease screening strategies in routine diabetes care.

RESULTS

The pleiotropic effects of thyroid hormones on various metabolic processes are now better understood. Uncontrolled hyperthyroidism in diabetic patients may trigger hyperglycaemic emergencies while recurrent hypoglycaemic episodes have been reported in diabetic patients with hypothyroidism. Furthermore, thyroid dysfunction may amplify cardiovascular disease risk in diabetic patients through inter-relationships with dyslipidaemia, insulin resistance and vascular endothelial dysfunction. However, the significance of subclinical degrees of thyroid dysfunction remains to be clarified. While these developments have implications for diabetic patients a consensus is yet to be reached on optimal thyroid screening strategies in diabetes management.

CONCLUSIONS

The increased frequency of thyroid dysfunction in diabetic patients and its likely deleterious effects on cardiovascular and metabolic function calls for a systematic approach to thyroid disease screening in diabetes. Routine annual thyroid testing should be targeted at diabetic patients at risk of thyroid dysfunction such as patients with T1DM, positive thyroid autoantibodies or high-normal TSH concentrations.