Serum TSH reference interval in healthy Finnish adults using the Abbott Architect 2000i Analyzer

Free thyroxine measurement in clinical practice: how to optimize indications, analytical procedures, and interpretation criteria while waiting for global standardization

Thyroid dysfunctions are among the most common endocrine disorders and accurate biochemical testing is needed to confirm or rule out a diagnosis. Notably, true hyperthyroidism and hypothyroidism in the setting of a normal thyroid-stimulating hormone level are highly unlikely, making the assessment of free thyroxine (FT4) inappropriate in most new cases. However, FT4 measurement is integral in both the diagnosis and management of relevant central dysfunctions (central hypothyroidism and central hyperthyroidism) as well as for monitoring therapy in hyperthyroid patients treated with anti-thyroid drugs or radioiodine. In such settings, accurate FT4 quantification is required. Global standardization will improve the comparability of the results across laboratories and allow the development of common clinical decision limits in evidence-based guidelines. The International Federation of Clinical Chemistry and Laboratory Medicine Committee for Standardization of Thyroid Function Tests has undertaken FT4 immunoassay method comparison and recalibration studies and developed a reference measurement procedure that is currently being validated. However, technical and implementation challenges, including the establishment of different clinical decision limits for distinct patient groups, still remain. Accordingly, different assays and reference values cannot be interchanged. Two-way communication between the laboratory and clinical specialists is pivotal to properly select a reliable FT4 assay, establish reference intervals, investigate discordant results, and monitor the analytical and clinical performance of the method over time.

Changing Immunochemistry Platforms: Thyroid Function Test Comparison and Reference Intervals Based on Clinical Needs

Background

Diagnosis of thyroid dysfunction relies on thyroid stimulating hormone (TSH), free thyroxine (FT4), and free tri-iodothyronine (FT3) tests against valid reference intervals (RIs). We changed the immunoassay platform from Abbott Architect to Siemens Atellica and aimed to establish Atellica RIs based on laboratory information system (LIS) patient data.

Methods

Atellica thyroid hormone immunoassays were verified against those of Architect. Real-life patient results were retrieved from LIS. A single result per patient dataset was used to establish the RIs by the indirect method.

Results

Atellica and Architect assays correlated well but Atellica showed a positive bias between 13% and 53%, the largest for FT4. Variations of the Atellica assays were ≤4%. The 95% Atellica RIs were 0.4–3.8 mU/L for TSH, 0.9–1.6 ng/dL for FT4, and 227–416 pg/dL for FT3. Considering the accumulating clinical experience with Atellica, the RIs for clinical use were adjusted as 0.5–4.0 mU/L, 0.9–1.8 ng/dL, and 169–409 pg/dL, respectively.

Conclusions

We verified thyroid hormone RIs for Atellica by the indirect method for the first time. Our model proved reliable for selecting results of presumably healthy individuals from LIS data. Critical review of the RIs with local endocrinologists is essential.

The pattern of TSH and fT4 levels across different BMI ranges in a large cohort of euthyroid patients with obesity

PURPOSE

A multifold association relates the hypothalamo-pituitary-thyroid axis to body weight. The potential underlying mechanisms are incompletely understood. Further, the mild severity of obesity and the small proportion of individuals with obesity in so far published cohort studies provide little insights on metabolic correlates of thyroid function in obesity.

METHODS

We retrospectively enrolled 5009 adults with obesity (F/M, 3448/1561; age range, 18-87 years; BMI range, 30.0-82.7 kg/m²), without known thyroid disease in a study on TSH and fT4 levels, lipid profile, glucose homeostasis and insulin resistance, anthropometric parameters including BIA-derived fat mass (%FM) and fat-free mass (FFM).

RESULTS

The overall reference interval for TSH in our obese cohort was 0.58-5.07 mIU/L. As subgroups, females and non-smokers showed higher TSH levels as compared to their counterparts (p<0.0001 for both), while fT4 values were comparable between groups. There was a significant upward trend for TSH levels across incremental BMI classes in females, while the opposite trend was seen for fT4 levels in males (p<0.0001 for both). Expectedly, TSH was associated with %FM and FFM (p<0,0001 for both). TSH and fT4 showed correlations with several metabolic variables, and both declined with aging (TSH, p<0.0001; fT4, p<0.01). In a subgroup undergoing leptin measurement, leptin levels were positively associated with TSH levels (p<0.01). At the multivariable regression analysis, in the group as a whole, smoking habit emerged as the main independent predictor of TSH (β=-0.24, p<0.0001) and fT4 (β=-0.25, p<0.0001) levels. In non-smokers, %FM (β=0.08, p<0.0001) and age (β=-0.05, p<0.001) were the main significant predictors of TSH levels. In the subset of nonsmokers having leptin measured, leptin emerged as the strongest predictor of TSH levels (β=0.17, p<0.01).

CONCLUSIONS

Our study provides evidence of a gender- and smoking-dependent regulation of TSH levels in obesity.

Factors influencing the reference interval of thyroid-stimulating hormone in healthy adults: A systematic review and meta-analysis

BACKGROUND

Many studies have reported that the thyroid-stimulating hormone (TSH) reference interval is susceptible to external factors, such as age, sex, race, region and iodine intake. However, no meta-analysis has comprehensively explored the effect of these factors on the TSH reference interval.

METHODS

Articles published from January 1960 to January 2020 were searched in PubMed, Embase, Cochrane, Scopus, Medline English databases and CNKI, WanFang and CQVIP Chinese databases. In total, 19 studies were ultimately included. All data were analysed using Review Manager 5.3, STATA 16.0 software, GraphPad Prism 8.0 and Microsoft Excel 2010 to draw the TSH concentration curve.

RESULTS

The TSH reference interval was significantly influenced by sex and age. The mean of TSH concentration in females was 0.27 mIU/L higher than that in males. Reference interval of TSH is divided into 20-59 years old and >60 years old age groups in males, and 20-39 years old and >40 years old age groups in females. Regardless of sex, TSH concentrations all increase with age. In iodine-deficient areas, TSH reference intervals were generally lower than those in iodine-sufficient or iodine-excessive areas. The TSH reference interval in Asia and North American countries was generally higher than that in most European countries. In the subgroup analyses of sample size, region and assay methods and manufacturers, the between-group differences were significant.

CONCLUSION

The TSH reference interval was significantly influenced by sex, age, iodine intake, sample size, region, and assay methods and manufacturers, but other factors should not be ignored. Therefore, it is necessary for each laboratory to validate an appropriate TSH reference interval based on local conditions.

Distributions of serum thyroid-stimulating hormone in 2020 thyroid disease-free adults from areas with different iodine levels: a cross-sectional survey in China

PURPOSE

The aim of the present study was to describe the distributions of serum thyroid- stimulating hormone (TSH) levels in thyroid disease-free adults from areas with different iodine levels in China. Meanwhile, we aimed to evaluate the influence of age and gender on the distribution of TSH, assess the relationship between concentrations of TSH and free thyroxine (FT₄), and analyze the factors that may affect TSH levels.

METHODS

2020 adults were included from April 2016 to June 2019. Urinary iodine concentration, serum iodine concentration, serum TSH, FT₄, free triiodothyronine, thyroid peroxidase antibodies and thyroglobulin antibodies were measured, and thyroid ultrasonography was performed.

RESULTS

The median of TSH in iodine-fortification areas (IFA), iodine-adequate areas (IAA), iodine-excessive areas (IEA) were 2.32, 2.11 and 2.34 mIU/L, respectively. Serum TSH concentrations were significantly higher in IFA and IEA than that in IAA (p = 0.005 and < 0.0001). The TSH values of most adults were distributed within the range of 1.01-3.00 mIU/L with the same trend in three groups. In our study, TSH levels did not change with age, and the TSH level of females was higher than that of males (p < 0.0001). There was a negative correlation between FT₄ and TSH in IAA (r = - 0.160, p < 0.0001) and IEA (r = - 0.177, p < 0.0001), but there was no correlation between FT₄ and TSH in IFA (r = - 0.046, p = 0.370). BMI, smoking status, education levels, and marital status were associated with TSH.

CONCLUSION

Our study provides a basis for establishing the reference intervals of TSH in different iodine level areas.

Impaired breathing, sleeping, vitality, and depression, and negative impact of L-T4 treatment characterize health-related quality of life in older people with stable CVD

BACKGROUND

Cardiovascular disease (CVD) and thyroid dysfunction are common in older people, but little is known about how they affect health-related quality of life (HRQoL).

METHODS

We assessed HRQoL with the 15D instrument in 329 home-dwelling patients aged ≥ 75 years with stable CVD and compared the results to those of an age- and gender-matched general population (n = 103). We also studied the impact of age, BMI, number of medications, thyroid-stimulating hormone (TSH) concentration, levothyroxine (L-T4) substitution and Mini-Mental State Examination (MMSE) on HRQoL.

RESULTS

Overall HRQoL was impaired in older people with stable CVD (mean 15D score 0.777 vs 0.801, p = 0.001), and also on single dimensions of breathing, sleeping, discomfort and symptoms, distress, vitality (all p < 0.001), and depression (p = 0.016) compared to the age- and gender-matched general population. Furthermore, in the patients, L-T4 substitution associated with impaired sleeping (p = 0.018) and sexual activity (p = 0.030). Moreover, MMSE points, number of medications used, age (all p < 0.001) and BMI (p = 0.009) predicted impaired HRQoL.

CONCLUSIONS

Older people with stable CVD are characterized by impaired HRQoL compared to age- and gender-matched controls. We demonstrate that this is the consequence of impaired breathing, sleeping, discomfort and symptoms, distress, vitality, and depression. L-T4 substitution has a negative impact on HRQoL in old patients with stable CVD. MMSE score, number of medications, age and BMI predict worse HRQoL.

Reference interval by the indirect approach of serum thyrotropin (TSH) in a Mediterranean adult population and the association with age and gender

Background The serum concentration of thyrotropin (TSH) represents a first-line test in diagnostic algorithms. The estimation of TSH reference intervals (RIs) is still a matter of debate due to the high prevalence of subclinical disease making difficult the definition of truly healthy subjects. The aim of this study was to estimate TSH RIs in healthy subjects and to evaluate the effect of age and gender on TSH concentration. Methods Forty-four thousand one hundred and fifty-six TSH data were collected between July 2012 and April 2018 at the Department of Laboratory Medicine, University-Hospital, Palermo. Common and sex-specific RIs were estimated by Arzideh's indirect method after exclusion of individuals younger than 15 years, subjects with repeated TSH tests and with abnormal free thyroxine (fT4), free triiodothyronine (fT3) or anti-thyroid-peroxidase antibodies. The combined effect of age and gender on TSH values was evaluated. Results RIs estimated in the selected individuals (n = 22602) were, respectively, 0.18-3.54 mIU/L (general), 0.19-3.23 mIU/L (men) and 0.18-3.94 mIU/L (women). Women showed significantly higher median TSH than men (1.46 vs. 1.39 mIU/L; p < 0.0001). Both in men and in women, median TSH decreased along with age; however, although up to 60 years in both men and women showed similar values, afterwards women showed constantly higher TSH than men. Accordingly, statistical analysis showed a significant interaction between gender and age (p = 0.001), suggesting that the effect of age on TSH is different between genders. Conclusions Our findings suggest that the indirect method, with appropriate cleaning of data, could be useful to define TSH RIs.

Reference Range and Sociodemographic Characteristics of TSH among Reproductive Age Women in Rural China

Appropriate reference range of thyroid-stimulating hormone (TSH) is important to interpreting the results of thyroid functional tests. However, the reference range and sociodemographic characteristics of TSH based on large-scale studies are yet to be declared in rural China. To clarify reference range and sociodemographic characteristics of TSH in reproductive age of women from rural China. A nationwide population-based study was conducted as The National Free Preconception Health Examination Project (NFPHEP). Nearly 400,000 (n = 392,659) of Chinese rural women aged 15-55 years were randomly recruited. Predetermined strict exclusion criteria made a number of 359,895 as the reference population. Serum TSH was evaluated with enzyme-linked immunosorbent assay (ELISA). The reference range of TSH on overall and reference population was 0.39-5.20 and 0.39-5.13 uIU/ml (2.5th-97.5th percentiles), respectively. In the reference population, the range (2.5th to 97.5th percentile) of serum TSH in different age groups was 0.40-5.03 uIU/ml, 0.39-5.15 uIU/ml, 0.37-6.10 uIU/ml, and 0.44-7.03 uIU/ml, respectively. The mean TSH value in women aged 26-35 years was 2.26 uIU/ml, significantly lower than those aged 36-45 (p < 0.001). The mean TSH values for eastern, central, and western regions were 2.28 uIU/ml, 2.29 uIU/ml, and 2.24 uIU/ml respectively. The mean of serum TSH concentration was significantly higher in central region than that in western region (p ≤ 0.001). The TSH value 0.39-5.13 uIU/ml (2.5th-97.5th percentiles) was derived as a reference range of reproductive age women from rural China. We use the TSH ranges from reference population to diagnose hyperthyrotropinemia or hypothyroidism in different areas in China. The reference ranges for eastern, central, and western regions were 0.33-5.61 uIU/ml, 0.40-5.04 uIU/ml, and 0.40-4.98 uIU/ml (2.5th-97.5th percentiles) respectively. The value of serum TSH was associated with age, living region, smoking, drinking, educational level, and interpersonal tension, as well as life and economic pressure, but irrelevant to ethnicity or occupation.

Age and Assay Related Changes of Laboratory Thyroid Function Tests in the Reference Female Population

Background

Laboratory thyroid function tests play a central role in the diagnosis of thyroid disorders. The aim of our cross-sectional study was to determine reference values for thyroid tests in a rigorously selected group of Montenegrin females, investigate the impact of possible age-related changes and the influence of the interassay bias between three frequently used immunoassays.

Methods

Female subjects were randomly selected, aged between 20 and 69 and 946 of them met the selection criteria. TSH, fT3, fT4, thyroid peroxidase and thyroglobulin antibodies were measured. Eighty samples were further analyzed on two other immunochemistry platforms.

Results

Median TSH progressively increased with age, there was no difference in fT3, while fT4 was significantly higher in the two oldest groups compared to the others. When using the age-related 97.5 percentile of TSH the percentage of reclassification was highest in the 20-29 years of age group (5.2%, p<0.05). In the oldest band, 7.7% had TSH values above cohort-specific and below the age-related upper reference limit. Bland-Altman bias plots revealed the highest interassay absolute mean difference between compared TSH assays of 24.5% and for fT4 assays of 13.8%.

Conclusions

The correlation coefficients between fT3 assays from different manufacturers were low. Serum TSH and fT4 concentrations increased with age and the implementation of age-specific TSH reference intervals would be of interest. The bias between the three commercial immunoassays indicated that the standardization of thyroid function tests is a task of great importance.

Reference intervals of thyroid hormones in Khartoum, Sudan

Objectives

This study aimed to establish the reference intervals (RIs) of thyroid function test among the adult Sudanese population in Khartoum, Sudan. A multi-stage survey stratified sampling method was used. Total triiodothyronine (TT3), total thyroxine (TT4) level and thyroid stimulating hormone (TSH) levels were measured using radioimmunoassay gamma counter (Riostad, Germany) to determine the reference intervals.

Result

A total of 390 adults aged 20–75 years (male: 40.5%, female: 59.5%) were recruited. The median (95% intervals) serum TSH, TT4 and TT3 levels were 1.2 (0.50–3.1) mIU/L, 103.0 (63.0–159.0) nmol/L and 1.4 (0.8–2.7) nmol/L respectively. Compared with males; females had significantly lower TSH level and significantly higher TT4 level, but there was no significant difference when the TT3 level was assessed. While there was no significant difference in the level of TSH and T3 in the age group, T4 levels have shown a progressive increase with age. In summary the RIs for TSH, TT4 and TT3 in this setting were different from the levels provided by the manufacturers. A significant different was observed in TSH and FT4 when considering gender issue. The RIs were not different in the different age groups except for FT4.

Reference intervals for thyrotropin in an area of Northern Italy: the Pordenone thyroid study (TRIPP)

PURPOSE

Thyrotropin (TSH) is the most accurate marker of thyroid dysfunction in the absence of pituitary or hypothalamic disease. Studies on TSH reference intervals (RIs) showed wide inter-individual variability and prompted an intense debate about the best estimation of TSH RIs.

DESIGN

We performed a population study on TSH RIs, using current data stored in the laboratory information system (LIS), at the Hospital Department of Laboratory Medicine, Pordenone (Italy), historically an area of mild-moderate iodine deficiency with a relatively high goiter prevalence.

METHODS

136,650 individuals constituted the final sample. A TSH immunoassay was performed on fasting serum samples with the Dimension Vista 1500 analyzer (Siemens Healthineers). We adopted the Kairisto's procedure to analyze TSH data downloaded by the LIS, applying the indirect strategy for deriving RIs.

RESULTS

TSH RIs of the entire population were 0.32-3.36 mIU/L with a distribution skewed towards higher values. RIs were 0.26-3.61 mIU/L for females, and 0.32-3.01 mIU/L for males. Unlike other studies, TSH median levels progressively decreased from 0-4 to 85-104 years in the overall population, both in male and in female subgroups, showing an inverse correlation between TSH and age in all groups.

CONCLUSIONS

This study is the first to analyze a high percentage (40%) of individuals from an ethnically homogenous Caucasian population. The results obtained emphasize the opportunity to define the TSH RIs according to age, gender and race, in addition to assay methods, and provide further insight about the possible role of iodine status.

Age- and gender-specific reference intervals of TSH and free T4 in an iodine-replete area: Data from Korean National Health and Nutrition Examination Survey IV (2013-2015)

BACKGROUND

Establishment of the reference interval of thyroid-stimulating hormone (TSH) is critical in the diagnosis of thyroid dysfunction and is affected by age, gender, iodine nutrition, and ethnicity. The aim of this study was to determine the reference intervals of TSH and free thyroxin (FT4) from a large, nationwide data of Korea where iodine intake is more than adequate.

METHODS

We analyzed data from the Korea National Health and Nutrition Examination Survey VI that measured serum TSH, FT4, and thyroid peroxidase antibody from 7,061 individuals (urinary iodine measurement in 6,565). Age- and gender-specific reference intervals were established from 95% confidence limits from the 2.5 to 97.5 percentile of TSH (log-transformed) and FT4 in reference populations.

RESULTS

The geometric mean of TSH was 2.16 ± 0.01 mIU/L, with the lowest value found in the middle aged group (2.04 ± 0.02 mIU/L) and higher values noted in age groups of 10-19 and over 70 years (2.38 ± 0.02 and 2.32 ± 0.07 mIU/L, respectively). The association of TSH and age was U-shaped. The overall reference interval of TSH was 0.59-7.03 mIU/L. Mean FT4 was 1.25 ± 0.003 ng/dL (16.09 ± 0.039 pmol/L), and it showed a small but continuous decrease after 20 years of age (P < 0.001). There was a significant positive correlation between TSH and urine iodine concentration (r = 0.154, P < 0.001).

CONCLUSIONS

The reference interval of TSH in Korea, where iodine intake is above the requirement, was 0.59-7.03 mIU/L and showed U-shaped change with age, which was a similar pattern to iodine intake. The reference interval of FT4 was 0.92-1.60 ng/dL. The geometric mean and upper limit of TSH were higher than those of Western populations, reflecting the paramount importance of iodine intake on thyroid function.

Using a thyroid disease-free population to define the reference interval for TSH and free T4 on the Abbott Architect analyser

OBJECTIVE

Thyroid disease can be subtle in its presentation, and TSH reference intervals may be artefactually increased by including persons with subclinical thyroid disease. We have therefore used a thyroid disease-free population to determine TSH and fT4 reference intervals.

DESIGN

Apparently healthy subjects were assessed by health questionnaire, drug history, clinical assessment and measurement of thyroid antibodies.

PATIENTS

Healthy subjects in a community setting.

MEASUREMENTS

TSH, free T4, antithyroglobulin and anti-TPO were measured on the Abbott Architect analyser. Subjects with clinical abnormalities, consumption of thyroid-active medications or with thyroid antibodies above the manufacturer-quoted reference intervals were excluded. TSH and fT4 data were log-transformed, and the central 95% was used to calculate reference intervals. We assessed whether these data were normally distributed. We compared samples spanning the reference intervals for both TSH and fT4 between different assays looking at biases.

RESULTS

From a population of 1,606 subjects, 140 males (18%) and 284 females (34%) were excluded. The central population 95% for TSH was 0·43-3·28 mU/l and for fT4 10·8-16·8 pmol/l. There were no age- or sex-related differences. For both analytes, the distribution was not significantly different to a Gaussian distribution (P > 0·05). For 5 commonly used assays for TSH, the maximum difference in the upper limit of the TSH reference interval was 0·48 mU/l and for fT4 the maximum difference for the upper reference limit was 4·1 pmol/l.

CONCLUSIONS

A substantial proportion of apparently healthy persons have subclinical thyroid disease. These subjects must be excluded for any thyroid hormone reference interval studies.

Monitoring the prevalence of thyroid disorders in the adult population of Northeast Germany

BACKGROUND

Only a few studies like ours have investigated the effect of long-term stable iodine supply on thyroid disorders in a historically iodine-deficient population, but not with a long follow-up time of 10 years.

METHODS

Data were derived from two independent population-based cohorts of the Study of Health in Pomerania (SHIP-0 [1997-2001] and SHIP-TREND [2008-2012]) comprising 4308 and 4420 subjects, respectively. Diagnosed thyroid disorders were assessed. Thyroid gland dimensions were examined by ultrasound. Levels of serum thyrotropin (TSH) and autoantibodies to thyroperoxidase (anti-TPO Abs) were measured from blood samples.

RESULTS

Median urinary iodine excretion levels decreased from 123.0 μg/l to 112.0 μg/l (p = <0.001) between 2000 and 2010. The prevalence of known thyroid disorders increased from 7.6 % [CI 6.9-8.5] to 18.9 % [CI 17.6-20.1] and of thyroid medication use from 6.2 to 11.1 %. The prevalence of goiter decreased from 35.1 to 29.4 % (p = <0.001), while the prevalence of positive anti-TPO Abs decreased from 3.9 to 2.9 % (p = 0.022). Median serum TSH levels increased from 0.69 mIU/L to 1.19 mIU/L (p = <0.001). Consequently, prevalence of high TSH (mIU/L) increased from 2.6 to 2.9 % (p = 0.452), and low TSH (mIU/L) decreased from 6.6 to 6.4 % (p = 0.737).

CONCLUSION

The decreased prevalence of iodine-deficient disorders and a stable prevalence of markers of autoimmune thyroid disorders argue for an improved iodine supply of the adult population in Northeast Germany. In contrast, the prevalence of diagnosed thyroid disorders and the intake of thyroid medication increased, although this might be related to inappropriate therapeutic decisions.

Serum thyroid-stimulating hormone and cognition in older people

BACKGROUND

high TSH concentrations and cognitive decline are both very common among older people and could be linked.

OBJECTIVE

to assess cognition in our cohort of 335 home-dwelling older people (75 years and older) and to cross-sectionally relate the results to thyroid-stimulating hormone (TSH) concentrations. Our special focus was on the upper normal TSH range and subclinical hypothyroidism.

METHODS

cognitive performance was evaluated using the Consortium to Establish a Registry for Alzheimer's disease neuropsychological battery (CERAD-nb). The Clinical Dementia Rating (CDR) scale was used to evaluate severity of cognitive disorder. The APOEε4 genotype was also defined. Subjects were divided into quartiles based on the TSH concentrations, and results were compared between these groups.

RESULTS

expected relations were observed between CERAD domains and both educational level and APOEε4 genotype. Female sex significantly associated with better performance in Boston naming (OR = 0.48; 95% CI = 0.27-0.85). In the whole cohort, higher TSH concentrations tended to associate with better scores in most parts of the CERAD-nb tests, but differences were not statistically significant. However, subjects with the highest TSH concentration (90th TSH percentile, range 4.14-14.4 mU/l) had better CDR scores compared with subjects with the lowest TSH concentration (10th percentile, range 0.001-0.63 mIU/l; OR 0.10; 95% CI 0.014-0.76).

CONCLUSIONS

our results do not support the notion that higher TSH concentrations, not even in the range of subclinical hypothyroidism, would adversely affect cognition among older people.

Shift of the TSH reference range with improved iodine supply in Northeast Germany

OBJECTIVE

Germany was iodine deficient until the mid-1990s when a nationwide iodine fortification program became effective. It is expected that after a longer period of sufficient iodine supply, median TSH values in the general population will shift to the right. Hence, the previous TSH reference range does not reflect the current TSH distribution in the general population of Germany. Thus, we aimed to establish a new reference range for serum TSH levels.

DESIGN AND METHODS

We used data from the Study of Health in Pomerania TREND, a population-based study including 4420 individuals. The reference population consisted of 1596 individuals without diagnosed thyroid diseases or thyroid-related findings in ultrasound and serum analysis. Serum TSH levels were measured by an immunochemiluminescent procedure on a Siemens Dimension Vista.

RESULTS

The overall reference range for TSH was 0.49 mIU/l (95% CI=0.44; 0.53)-3.29 mIU/l (95% CI=3.08; 3.50). The lower reference limit differed significantly by sex, whereas the upper reference limit showed no significant difference between males and females. Age was significantly associated with the 2.5th TSH percentile in males but not in females, whereas age was significantly associated in males and females for the 97.5th TSH percentile.

CONCLUSIONS

We demonstrate a shift toward the right of the TSH reference range in comparison with data from the same study region 10 years earlier, which is likely due to the improved iodine supply of the study region. Our study indicates that TSH reference limits are dependent on past and current iodine supply of populations.

Establish and verify TSH reference intervals using optimized statistical method by analyzing laboratory-stored data

OBJECTIVE

To establish reference intervals using an optimized statistical method by collecting available laboratory data of thyroid stimulating hormone (TSH), and then to verify with the laboratory-present reference intervals.

METHODS

TSH RIs of the total population and different races, genders, age, source of sample are established through improved Hoffmann and Katayev's method with TSH test results data from Jan 2010 to April 2012 were collected, and finally conduct comparative verification with the laboratory present RIs.

RESULTS

According to the improved method, we get various RIs of different sample populations. On comparing with the laboratory current RI (0.270-4.200 mIU/L) most reference change values (RCV) were within acceptable limits. Only lower limit of Han male, Uygur male and out-patient male populations outwith acceptable limits. On excluding the different values, finally, the new RI by the optimized statistical method is 0.233-4.979 mIU/L. Because the new RI expanded the current RI and was not different from the current RI, it was indicated that new RI could be used to verify the laboratory current RIs and seen as the current RI's confidence interval (CI).

INFERENCE

TSH RIs established by optimized Hoffmann's and Katayev's methods is viable and can be used to verify RIs provided by manufacturers or other laboratories.

Reference limit of thyrotropin (TSH) and free thyroxine (FT4) in thyroperoxidase positive and negative subjects: a population based study

BACKGROUND

Current reference values for thyroid function tests are based on data from different ethnicities and geographical areas. The aim of the present study was to determine reference intervals for thyrotropin (TSH) and free T4 (FT4), based on the criteria of the National Academy of Clinical Biochemistry (NACB) in an Iranian population.

MATERIAL AND METHODS

This study was conducted within the framework of Tehran Thyroid Study (TTS), an ongoing prospective cohort of 5704 randomly selected individuals, age ≥ 20 yr. A total of 2199 individuals (43.3% male, 56.7% female), based on NACB criteria were included in this study. Reference limit analysis was performed for the negative thyroid peroxidase antibody (TPOAb) group.

RESULTS

After applying all exclusion criteria except TPOAb positivity (10.5%), data of 2459 participants remained for analysis. Of these, 953 (43.3%) were males and 1246 (56.7%) were females; the mean ± SD age was 43.53 ± 14.16 yr. The mean ± SD and median+IQR for TSH were 1.77 mU/l ± 1.24 and 1.46 (0.93-2.23) mU/l, respectively. The 2.5th and 97.5th percentiles TSH were 0.32 mU/l and 5.06 mU/l respectively. The mean ± SD and median (IQR) for FT4 for all negative TPOAb subjects were 1.19 ± 0.16 and 1.18 (1.08-1.31) ng/dl respectively.

CONCLUSION

Reference ranges for thyroid function tests need to be derived from national databases. This study determined age and sex specific TSH and FT4 reference ranges in a Tehranian population, which could eventually enable clinicians to classify patients more appropriately.

Marked Biological Variance in Endocrine and Biochemical Markers in Childhood: Establishment of Pediatric Reference Intervals Using Healthy Community Children from the CALIPER Cohort

BACKGROUND

Reference intervals are indispensable in evaluating laboratory test results; however, appropriately partitioned pediatric reference values are not readily available. The Canadian Laboratory Initiative for Pediatric Reference Intervals (CALIPER) program is aimed at establishing the influence of age, sex, ethnicity, and body mass index on biochemical markers and developing a comprehensive database of pediatric reference intervals using an a posteriori approach.

METHODS

A total of 1482 samples were collected from ethnically diverse healthy children ages 2 days to 18 years and analyzed on the Abbott ARCHITECT i2000. Following the CLSI C28-A3 guidelines, age- and sex-specific partitioning was determined for each analyte. Nonparametric and robust methods were used to establish the 2.5th and 97.5th percentiles for the reference intervals as well as the 90% CIs.

RESULTS

New pediatric reference intervals were generated for 14 biomarkers, including α-fetoprotein, cobalamin (vitamin B12), folate, homocysteine, ferritin, cortisol, troponin I, 25(OH)-vitamin D [25(OH)D], intact parathyroid hormone (iPTH), thyroid-stimulating hormone, total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), and free triiodothyronine. The influence of ethnicity on reference values was also examined, and statistically significant differences were found between ethnic groups for FT4, TT3, TT4, cobalamin, ferritin, iPTH, and 25(OH)D.

CONCLUSIONS

This study establishes comprehensive pediatric reference intervals for several common endocrine and immunochemical biomarkers obtained in a large cohort of healthy children. The new database will be of global benefit, ensuring appropriate interpretation of pediatric disease biomarkers, but will need further validation for specific immunoassay platforms and in local populations as recommended by the CLSI.

Maternal thyroid dysfunction during pregnancy and thyroid function of her child in adolescence

CONTEXT

Normal maternal thyroid function is important for fetal development. No knowledge exists on how maternal thyroid function and thyroid antibodies during early pregnancy affect thyroid function of the offspring.

OBJECTIVE

The aim of this study was to investigate the relationship between maternal and adolescent thyroid function parameters.

DESIGN, SETTING, AND PARTICIPANTS

A total of 3673 mother-child pairs from the prospective, population-based Northern Finland Birth Cohort 1986 participated in the study. Maternal serum samples were drawn in early pregnancy (<20th gestational week), and children's samples were drawn at the age of 16 years and analyzed for TSH, free T4 (fT4), and thyroid peroxidase antibodies (TPO-Abs).

MAIN OUTCOME MEASURES

TSH, fT4, and TPO-Ab concentrations were measured at the age of 16 years. Children of mothers with thyroid dysfunction (hypothyroidism, hyperthyroidism, or hypothyroxinemia) or TPO-Ab positivity were compared to those of euthyroid or TPO-Ab-negative mothers. The distributions are expressed as medians with 5th to 95th percentiles.

RESULTS

Boys of hypothyroid mothers had higher TSH concentrations than those of euthyroid mothers: 2.0 (0.9-4.0) vs 1.7 (0.8-3.3) mU/L; P = .001. Children of hyperthyroid mothers had lower TSH concentrations than those of euthyroid mothers: 1.3 (0.6-4.2) vs 1.7 (0.8-3.3) mU/L, P = .013, for boys; and 1.3 (0.5-3.5) vs 1.6 (0.7-3.4) mU/L, P = .034, for girls. There were no differences in TSH or fT4 concentrations between children of hypothyroxinemic and euthyroid mothers. TPO-Ab-positive mothers more often had TPO-Ab-positive children (prevalence, 9.0 vs 3.7% among boys, and 22.7 vs 7.5% among girls).

CONCLUSIONS

Maternal thyroid dysfunction and TPO-Ab positivity during pregnancy seem to modify thyroid function parameters of offspring even in adolescence. Whether this increases the thyroid disease risk of the children is still unknown.

Reference intervals on the Abbot Architect for serum thyroid hormones, lipids and prolactin in healthy children in a population-based study

Pediatric reference intervals for thyroid hormones, prolactin and lipids are of high clinical importance as deviations might indicate diseases with serious consequences. In general, previous reference intervals are hampered by the inclusion of only hospital-based populations of children and adolescents. The study included 694 children, evenly distributed from 6 months to 18 years of age. They were recruited as volunteers at child care units and schools. All subjects were apparently healthy and a questionnaire on diseases and medications was filled out by parents and by the older children. TSH, free T4, free T3, total cholesterol, LDL, HDL, triglycerides and prolactin were analyzed on Abbott Architect ci8200. Age- and gender-related 2.5 and 97.5 percentiles were estimated. The thyroid hormone levels were similar to previous data for the Abbott Architect platform, but exhibited differences from studies performed with other methods. Prolactin displayed wide reference ranges, but relatively small age-related changes, and a marginal difference between sexes during adolescence. Reference intervals for lipids in the different age groups are known to vary geographically. Levels of LDL and total cholesterol were higher than those reported for children in Canada, but lower than those reported for children in China. The study gives age- and gender- specific pediatric reference intervals, measured with modern methods for a number of important analytes. The results presented here differ from previously recommended reference intervals. In many earlier studies, retrospective hospital-based reference intervals, which may include various sub-groups have been presented. By non-hospital studies it is possible to avoid some of these biases.