Month of birth is associated with the subsequent diagnosis of autoimmune hypothyroidism. A nationwide Danish register-based study

BACKGROUND

The triggering of thyroid autoimmunity in the genetically susceptible remains a conundrum. Environmental exposures during gestation and/or early postnatally have proponents, as suggested in diabetes mellitus, with a higher incidence of births during spring and summer. Whether the development of autoimmune hypothyroidism (AIT) is influenced by month or season of birth is less clear.

METHOD

Nationwide cohort study of 111 565 individuals diagnosed with AIT and four euthyroid controls per case, matched according to age and sex, were identified from Danish health registers. Differences in month of birth across the year were evaluated by the Walter-Elwood test. The risk of patients with AIT being born in a certain month or season of the year was calculated using a Cox regression model.

RESULTS

There was a significant difference in birth month between cases and controls, P<.001. Individuals with AIT had a significantly increased risk of being born in June (Hazard ratio 1.04; 95% Confidence interval (CI): 1.02-1.08) and in the summer (June-August; HR 1.02; 95%CI: 1.01-1.04).

CONCLUSION

In this large-scale nationwide cohort study, we found a higher risk of AIT when born in the summer season or more specifically in June, supporting the hypothesis that seasonal variations in exposures-gestationally and/or early postnatally-may contribute to the development of AIT.

Chronic autoimmune disorders are increased in coeliac disease: A case-control study

Coeliac disease (CD) is an autoimmune disorder of the small bowel associated with increased risk of additional autoimmune diseases (ADs).To investigate the prevalence of ADs in a population of adult coeliac patients.This was a retrospective case-control study. Data from coeliac patients and controls referred to a tertiary center between 2013 and 2016 were collected. The frequency of ADs and the unadjusted and adjusted odds ratios (ORs) for age, gender, disease duration, and body mass index with their 95% confidence intervals (CIs) were evaluated.Two hundred fifty-five patients with CD (median age 37.1 years; 206 women) were matched with 250 controls. ADs were more frequent (35.3%) in coeliac patients than in controls (15.2%). Adjusted ORs for the presence of only 1, at least 1, and more than 1 AD were 3.13 (95% CI 1.81-5.42, P < .0001), 3.31 (95% CI 2.00-5.46, P < .0001), and 3.93 (95% CI 1.49-10.36, P = .006), respectively. Hashimoto thyroiditis was the most prevalent AD (24.3% vs. 10%) OR = 2.55 (95% CI 1.39-4.70, P < .0001), followed by psoriasis (4.3% vs. 1.6%), type 1 diabetes (2.7% vs. 0.4%), and Sjögren syndrome (2.4% vs. 0.4%).These findings suggest a need for a careful surveillance of autoimmune status, especially for Hashimoto thyroiditis in patients with celiac disease.

The polymorphisms in the thyroid peroxidase gene were associated with the development of autoimmune thyroid disease and the serum levels of anti-thyroid peroxidase antibody

Graves' disease (GD) and Hashimoto's disease (HD) are well known autoimmune thyroid diseases (AITDs), and the severity and intractability of AITDs varies among patients. Thyroid peroxidase (TPO) is a thyroid-specific antigen. The levels of anti-thyroid peroxidase antibody (TPOAb) were higher in patients with HD and may be associated with thyroid destruction. In this study, we genotyped eight single nucleotide polymorphisms (SNPs) in the TPO gene to clarify the association of TPO gene polymorphisms with the development, severity and intractability of AITD. We genotyped TPO rs2071399G/A, rs2071400C/T, rs2071402A/G, rs2071403A/G, rs1126799C/T, rs1126797T/C, rs732609A/C, and rs2048722A/G polymorphisms in 145 patients with GD, 147 patients with HD and 92 healthy controls by PCR-RFLP method. TPO rs2071400 T carriers (CT + TT genotypes) were more frequent in AITD, GD, and HD patients (p=0.0079, 0.0041, and 0.0488, respectively). The TPO rs2071403 GG genotype was more frequent in AITD, GD, and HD patients (p=0.0227, 0.0465, and 0.0305, respectively). There was no significant association between the SNPs and the prognosis of AITD. Serum levels of TPOAb were significantly higher in AITD patients with TPO rs2071400 T carriers (CT + TT genotypes) than in those with the CC genotype (p=0.0295), and were also significantly higher in AITD patients with TPO rs2048722 T carriers (CT + TT genotypes) than in those with the CC genotype (p=0.0056). In conclusion, TPO rs2071400 and rs2071403 polymorphisms were associated with the development of HD and GD, but not with the prognosis. Moreover, TPO rs2071400 and rs2048722 polymorphisms were associated with the serum levels of TPOAb.

Hashimoto's thyroiditis: relative recurrence risk ratio and implications for screening of first-degree relatives

CONTEXT

The relative recurrence risk ratio (λ_R ) for Hashimoto's thyroiditis (HT) has not been widely studied. The age at which thyroid function evaluation should be initiated for relatives of HT patients remains unclear.

OBJECTIVE

To study λ_R and age-related prevalence of HT in first-degree relatives of HT patients.

METHODS

First-degree relatives (n = 861) of 264 HT patients were evaluated for goitre, thyroid function tests, thyroid antibodies (TAb) and urinary iodide concentration (UIC). HT was defined as TAb positivity and hypothyroidism (subclinical/overt). λ_R was calculated as {number of index patients whose relatives (of particular subtype) had HT/number of index patients having relatives of same subtype}÷ population prevalence of HT (5·1%). The age-related prevalence of HT was studied using Kaplan-Meier method.

RESULTS

A total of 861 relatives (205 parents, 336 siblings and 320 offspring) participated in the study. About 38·3% were TAb positive. The prevalence of HT was 16·7% (22·9% in parents, 19·6% in siblings and 9·6% in offspring). TAb positivity (48·3% vs 33·1%) and HT (23·5% vs 13·6%) were significantly more common in the goitrous group (n = 267) vs nongoitrous group. The median UIC for the study population was 182·5 μg/l. Computed λ_R was 9·1 for any one relative being affected, 5·9 for parents, 6·3 for siblings and 3·1 for offspring. The prevalence of HT increased with age and exceeded the adult population prevalence of 5·1% at 20 years in females and 27 years in males.

CONCLUSIONS

Relatives of HT patients have a ninefold increased risk for developing HT as compared to the general population. The risk of developing HT exceeds that of the general population at 20 years in females and 27 years in males.

Diplopia in a patient with Hashimoto's thyroiditis: A case report and literature review

BACKGROUND

A case report of Hashimoto's thyroiditis-associated ophthalmopathy that masqueraded as double elevator palsy in 1 eye.

CASE PRESENTATION

A 54-year-old woman presented to our strabismus clinic with diplopia for 1 year. She was diagnosed with double elevator palsy in the left eye. The forced duction test yielded positive findings for the inferior rectus of the left eye; hence, computed tomography of the orbit and thyroid-associated blood tests were performed; surprisingly, the thyroid function test results were consistent with hypothyroidism and the antibody results such as antithyroglobulin and antithyroid peroxidase were markedly elevated, and the patient was diagnosed with Hashimoto's thyroiditis and treated with corticosteroids. Unfortunately, her diplopia was not relieved with medical management. Subsequently, a 9-mm left inferior rectus recession was performed.

CONCLUSION

Clinicians should be aware of the atypical signs of Hashimoto's thyroiditis for its proper diagnosis and management.

You're the Flight Surgeon

McLaughlin CM. You're the flight surgeon: atypical hypothyroid presentation. Aerosp Med Hum Perform. 2017; 88(5):509-511.

Myxedema coma: A case report of pediatric emergency care

RAIONALE

Myxedema coma (MC) is extremely rare but lethal in pediatric patients with hypothyroidism leading to altered mental status and hypothermia. But there is no clinical guideline for such cases.

PATIENT CONCERNS

A 6-year-old Chinese girl presented with coma and hypothermia preceded by pneumonia. Her lab results were: free thyroxin (T4) 4.18 pmol/L and thyroid-stimulating hormone (TSH) > 150 μIU/mL with extremely elevated anti-thyroid peroxidase (TPO-Ab) and anti-thyroglobulin. Pneumonia, mild pleural, and pericardial effusion were seen on computed tomographic (CT) scan.

DIAGNOSES

MC, autoimmune hypothyroidism, pneumonia and sepsis were diagnosed.

INTERVENTION

Gastric levothyroxine, intravenous dexamethasone and antibiotics were administered.

OUTCOME

Her consciousness was restored and temperature returned to normal 2 days after starting levothyroxine. She was discharged two weeks later.

CONCLUSION

MC is rare but may be the initial presentation in pediatric patients with prolonged untreated hypothyroidism. Autoimmune thyroiditis could cause hypothyroidism in children. MC should be suspected in pediatric patients with altered mental status, hypothermia and cardiovascular instability. Treatment with 100 mg/m of gastric levothyroxine is an option for pediatric patients with MC.

Mulberry cells in the thyroid: warthin-finkeldey-like cells in hashimoto thyroiditis-associated lymphoma

Warthin-Finkeldey type giant cells were first described in autopsies performed on young children who died during the highly lethal measles epidemic in Palermo during the winter of 1908. The cells had 8-15 nuclei without identifiable cytoplasm within the germinal centers of lymphoid organs resembling megakaryocytes. We describe a case of Hashimoto thyroiditis with an enlarging substernal throid mass. The resection specimen contained many Warthin-Finkeldey-Like Cells (WFLC) in an extranodal marginal zone lymphoma (MALT type) with focal transformation to diffuse large B-cell lymphoma. The WFLC showed nuclear features similar to those of neighboring follicular dendritic cells (FDCs), favoring the hypothesis that these cells might be the product of fusion of FDCs. This is supported by immunostaining results and the occurrence of similar cells in follicular dendritic cell sarcomas and in "dysplastic" FDCs in hyaline vascular type Castleman disease, a possible precursor of follicular dendritic cell tumors. Diagn. Cytopathol. 2017;45:212-216. © 2016 Wiley Periodicals, Inc.

Riedel's thyroiditis association with IgG4-related disease

CONTEXT

IgG4-positive (+) plasma cells have been reported in both Riedel's thyroiditis (RT) and Hashimoto's thyroiditis (HT). These cells are the hallmark of IgG4-related disease (IgG4-RD).

OBJECTIVE

We sought to determine whether RT is part of IgG4-RD spectrum.

DESIGN, SETTING AND PATIENTS

This was a case-control study performed at a tertiary medical centre. We included RT cases from the period 1958 to 2008 that had sufficient paraffin-embedded tissue for IgG4 immunostaining. Controls were patients with HT, age and gender matched, with similar pathology criteria.

MAIN OUTCOME MEASURE

The main outcome measures were the intensity of the IgG4 staining and the clinical and histological correlates with IgG4-RD.

RESULTS

Six pairs of RT and HT were analysed. The mean age was 44·7 years. In both groups, 5/6 cases had positive IgG4 staining. The mean number of IgG4 + cells/ HPF, normalized to the degree of inflammation, was 3·2 ± 3·0 SD (RT) vs 0·9 ± 0·7 (HT), P = 0·15, for fibrotic areas and 2·1 ± 2·3 SD vs 1·0 ± 0·8 (P = 0·39) for areas with lymphoid aggregates. We found the number of IgG4 +  cells in RT to be inversely correlated with the duration of disease (P = 0·046). Three RT cases had associated comorbidities from the IgG4-RD spectrum while none of the HT cases had such conditions.

CONCLUSIONS

Riedel's thyroiditis is a component of IgG4-RD with the density of the IgG4 +  lymphocytic infiltrate being time dependent. In this small study, we did not identify differences in IgG4 infiltration between RT and HT, minimizing the utility of this marker in RT diagnosis.

Autoimmune comorbidities in Hashimoto's thyroiditis: different patterns of association in adulthood and childhood/adolescence

OBJECTIVE

Hashimoto's thyroiditis (HT), the most common autoimmune thyroid disease at any age, is often associated with other autoimmune diseases. The present study was aimed to describe the type and frequency of non-thyroidal autoimmune diseases (NTADs) in HT patients and to delineate the clinical pattern of diseases clustering in pediatric/adolescent and adult age.

DESIGN

Cross-sectional study.

METHODS

1053 newly diagnosed HT patients (500 adults (467 F, mean age 40.2 ± 13.7 years) and 553 children/adolescents (449 F, mean age 11.1 ± 3.0 years)) were evaluated for common NTADs by means of careful recording of medical history, physical examination and assessment of selected autoantibody profiles.

RESULTS

The prevalence of associated NTADs was significantly higher in adults than that in pediatric/adolescent HT patients (P < .0001). In addition, the number of adult patients suffering from two or more associated NTADs was significantly higher than that of children/adolescent (P < 0.0001). A female prevalence was evident in both cohorts, but was significant in the adults (P < 0.0001). The epidemiological distribution of NTADs was strongly different in the two cohorts, the most frequent associated diseases being arthropathies and connective tissue diseases in adults and type 1 diabetes and coeliac disease in children/adolescents. Skin diseases were represented with similar prevalence in both cohorts, vitiligo being the most common.

CONCLUSIONS

Age at HT presentation may influence autoimmune diseases clustering, favoring the association of specific NTADs in different ages of life. Moreover, the association between HT and NTADs increases with age and occurs most frequently in adults.

Unfavorable Course of Subclinical Hypothyroidism in Children with Hashimoto's Thyroiditis Compared to Those with Isolated Non-Autoimmune Hyperthyrotropinemia

Subclinical hypothyroidism (SCH) is a common problem in pediatric population, and the natural history of SCH varies depending on its etiology. Whether Hashimoto's thyroiditis (HT) negatively affects the natural course of SCH was investigated in pediatric patients without concomitant diseases. Predictors for levothyroxine medication were also evaluated. Medical records of 109 children with SCH (91 girls, 5?18 years) diagnosed between 2005 and 2014 were retrospectively reviewed. Patients were classified into HT (n = 37) and isolated non-autoimmune hyperthyrotropinemia (iso-NAHT, n = 72). During median 2 years of follow-up, only 10.1% of SCH patients eventually initiated levothyroxine, and HT patients showed a higher probability of requiring levothyroxine medication than iso-NAHT patients (21.6% vs. 4.2%). Underlying HT independently predicted deterioration of thyroid function, leading to levothyroxine medication (hazard ratios [HRs], 4.6 vs. iso-NAHT, P = 0.025). High titers of anti-thyroglobulin antibodies (TGAbs) predicted later medication in the HT group (HRs, 28.2 vs. normal TGAbs, P = 0.013). Most pediatric SCH showed benign and self-remitting courses. Underlying HT significantly increases the risk for levothyroxine medication, especially with high titers of TGAbs.

Co-Existence of Thyroid Nodule and Thyroid Cancer in Children and Adolescents with Hashimoto Thyroiditis: A Single-Center Study

BACKGROUND

Currently, there is an inadequate number of studies on nodule and malignancy development in children and adolescents with Hashimoto thyroiditis (HT).

MATERIAL AND METHODS

Patients who were diagnosed with HT between 2004 and 2013 were included in the study. The HT diagnosis was made with a heterogeneous appearance on thyroid ultrasonography and the elevation of antithyroid peroxidase and/or anti-thyroglobulin antibodies. Fine-needle aspiration biopsy (FNAB) was performed in cases with a nodule size >1 cm or who had ultrasonography findings indicating malignancy.

RESULTS

A total of 39 (13%) thyroid nodules were detected in 300 patients with a diagnosis of HT. Papillary thyroid carcinoma (PTC) was diagnosed in 2 of the 12 cases in whom FNAB was performed. The thyroid nodule was detected at the same time as HT in the 2 cases with malignancy. The PTC diagnosis was made 2 years after the HT diagnosis in the first case and 3 years later in the second case. The largest diameter of the thyroid nodule was 5 mm in both cases.

CONCLUSION

The thyroid nodule rate on an HT background was found to be 13%, and the thyroid malignancy rate was 0.67% in our study.

Using Hashimoto thyroiditis as gold standard to determine the upper limit value of thyroid stimulating hormone in a Chinese cohort

BACKGROUND

Subclinical hypothyroidism, commonly caused by Hashimoto thyroiditis (HT), is a risk factor for cardiovascular diseases. This disorder is defined as merely having elevated serum thyroid stimulating hormone (TSH) levels. However, the upper limit of reference range for TSH is debated recently. This study was to determine the cutoff value for the upper normal limit of TSH in a cohort using the prevalence of Hashimoto thyroiditis as "gold" calibration standard.

METHODS

The research population was medical staff of 2856 individuals who took part in health examination annually. Serum free triiodothyronine (FT3), free thyroxine (FT4), TSH, thyroid peroxidase antibody (TPAb), thyroglobulin antibody (TGAb) and other biochemistry parameters were tested. Meanwhile, thyroid ultrasound examination was performed. The diagnosis of HT was based on presence of thyroid antibodies (TPAb and TGAb) and abnormalities of thyroid ultrasound examination. We used two different methods to estimate the cutoff point of TSH based on the prevalence of HT.

RESULTS

Joinpoint regression showed the prevalence of HT increased significantly at the ninth decile of TSH value corresponding to 2.9 mU/L. ROC curve showed a TSH cutoff value of 2.6 mU/L with the maximized sensitivity and specificity in identifying HT. Using the newly defined cutoff value of TSH can detect patients with hyperlipidemia more efficiently, which may indicate our approach to define the upper limit of TSH can make more sense from the clinical point of view.

CONCLUSIONS

A significant increase in the prevalence of HT occurred among individuals with a TSH of 2.6-2.9 mU/L made it possible to determine the cutoff value of normal upper limit of TSH.

Autoimmune Epilepsy

PURPOSE OF REVIEW

This review presents recent developments in the clinical features, immunologic basis, and treatment options for autoimmune encephalitis, seizures, and epilepsy.

RECENT FINDINGS

In addition to the expansion of our knowledge on classic paraneoplastic limbic encephalitis with onconeural antibodies, recent years have witnessed the development of the category of encephalitis associated with antibodies directed toward neuronal surface antigens. Antibodies against the voltage-gated potassium channel are, in fact, directed toward an array of targets within a large molecular complex. The most common target, leucine-rich, glioma inactivated 1 (LGI1), is associated with a syndrome of limbic encephalitis, sometimes preceded by disease-specific faciobrachial dystonic seizures, which could allow early diagnosis and treatment. Encephalitis with N-methyl-D-aspartate (NMDA) receptor antibodies, only discovered a few years ago, has emerged as the leading syndrome of this new category. Its clinical features and EEG signature are well defined, which should allow prompt recognition and treatment. The list of antibodies is still growing as new antibodies are identified that recognize other synaptic proteins, such as the γ-aminobutyric acid (GABA), α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), and glycine receptors. The role of glutamic acid decarboxylase 65 (GAD65) antibodies is still a controversy, as is the cause of Rasmussen encephalitis and syndromes of cryptogenic refractory status epilepticus and the mechanisms of seizures in systemic autoimmune diseases. A link between autoimmunity and epilepsy has been substantiated by large epidemiologic studies, but the nature of the causality requires more research.

SUMMARY

Autoimmune encephalitis is an important cause of seizures to recognize as it entails a specific therapeutic approach. Paraneoplastic limbic encephalitis and NMDA receptor and LGI1 encephalitis are well-characterized immunoclinical associations. Other syndromes and antibodies are being actively identified and described. A concept of autoimmune epilepsy is emerging and, if confirmed, is likely to alter the therapeutic approach and improve the outcome of some patients with pharmacoresistant epilepsy.

Five-Year Prospective Evaluation of Thyroid Function Test Evolution in Children with Hashimoto's Thyroiditis Presenting with Either Euthyroidism or Subclinical Hypothyroidism

BACKGROUND

Whether the course of thyroid function in Hashimoto's thyroiditis (HT) differs in children who present with either euthyroidism or subclinical hypothyroidism (SH) has been incompletely investigated.

AIM

Using a five-year prospective evaluation of 234 children with HT and no prognostic risk factors, this study investigated whether the evolution of the thyroid status is influenced by the biochemical pattern at initial diagnosis.

RESULTS

In the entire series, thyrotropin values significantly increased during follow-up, while free thyroxine values decreased and the proportion of children with a thyroid dysfunction increased from 27.3% to 47.4% (p = 0.0001). An increasing proportion of cases with severe thyroid dysfunction was identified, especially among the 64 patients presenting with SH (group B), but also among the 170 children presenting with euthyroidism (group A) at initial diagnosis. At the end of follow-up, the prevalence of children with overt hypothyroidism was 12.3% in group A compared with 31.2% in group B (p = 0.0007). In the overall population, however, the majority of patients (52.6%) exhibited biochemical euthyroidism at the end of follow-up.

CONCLUSIONS

Children with HT may develop a deterioration of thyroid status during the first five years of disease. Such a trend may be observed, even in the patients who initially present with a mild biochemical picture (either SH or euthyroidism). A total of 57.1% of initially euthyroid children remain euthyroid, and 40.6% of patients with initial SH normalize thyroid function within five years after HT diagnosis. The patients presenting with SH are more prone to the risk of developing severe thyroid dysfunction over time.

Low vitamin D status is associated with hypothyroid Hashimoto's thyroiditis

OBJECTIVE

The association of low vitamin D status with autoimmune thyroid disease (AITD), which includes Hashimoto's thyroiditis (HT) and Graves' disease (GD), is controversial. The aim of this study was to investigate the correlation between vitamin D insufficiency and AITD, HT, and GD.

DESIGN

Our cross-sectional study included patients who visited a tertiary hospital for thyroid evaluation or follow-up. A total of 776 patients in whom serum 25-hydroxyvitamin D [25(OH)D], thyroid function, and anti-thyroid antibodies had been measured were analyzed retrospectively. Vitamin D insufficiency was defined as serum 25(OH)D level <75 nmol/L.

RESULTS

The prevalence of vitamin D insufficiency was significantly higher in the 369 patients with AITD than in the 407 without AITD (46.1% vs. 37.1%, p=0.011), and higher in the 221 patients with HT than in those with GD or non-AITD (48.9% vs. 41.9%, 37.1%, p=0.017). Among HT cases, patients with overt hypothyroidism had a significantly higher prevalence of vitamin D insufficiency (60.4% vs. 44.1%, 21.7%, 37.1%, respectively, p <0.001) and lower 25(OH)D levels (80.1 ± 47.7 vs. 99.34 ± 61.2, 110.3 ± 69.9, 99.6 ± 53.7 nmol/L, respectively, p=0.009) compared with those with euthyroidism and subclinical hypothyroidism or those without AITD. Serum 25(OH)D levels were significantly negatively correlated with serum thyroid stimulating hormone (TSH) levels after adjustment for age, sex, body mass index, and sampling season (r= -0.127, p=0.013).

CONCLUSION

Vitamin D insufficiency was associated with AITD and HT, especially overt hypothyroidism. Low serum vitamin D levels were independently associated with high serum TSH levels.

Case Studies in Neurocritical Care

The practice of neurocritical care encompasses multiple acute neurologic and neurosurgical diseases and requires detailed knowledge of neurology and critical care. This article presents 5 cases that illustrate just some of the conditions encountered in the daily practice of neurocritical care and exemplify some of the common diagnostic, therapeutic, and prognostic challenges facing the neurointensivist. Life-threatening medical complications after severe acute ischemic stroke, seizures and extreme agitation from autoimmune encephalitis, refractory seizures after subdural hemorrhage, neurologic and systemic complications related to aneurysmal subarachnoid hemorrhage, and status epilepticus after cardiac arrest are discussed in this article.

Key-role of thyrotropin deficiency in disclosing craniopharyngioma diagnosis in a short girl with Hashimoto's thyroiditis

In a short girl with celiac disease and Hashimoto's thyroiditis (HT), suspicion of an associated pituitary lesion was suggested by the finding of a thyroid function pattern that was not compatible with HT-related hypothyroidism (low FT4 with normal TSH). This case report reinforces the view that the finding of a normal TSH in presence of a low FT4 should always alert pediatricians and raise suspicion of central hypothyroidism, even when a primary thyroid disease has been already identified. In this case TSH deficiency played a critical role in disclosing diagnosis of craniopharyngioma (CP). Therefore, the subsequent work-up was directed towards investigating pituitary function and morphology. Endocrinological investigations evidenced a picture of TSH and other pituitary hormone deficiency, whereas magnetic resonance imaging revealed an intrasellar CP. Therefore, in this case TSH deficiency played a key-role in disclosing CP diagnosis.

Immunoassay of thyroid peroxidase autoantibodies: diagnostic performance in automated third generation methods. A multicentre evaluation

BACKGROUND

The use of automated immunometric methods for the detection of anti-thyroid peroxidase antibodies (TPOAb), the main serological marker of autoimmune thyroid diseases (AITD), has expanded in recent years. However, it is not known whether these new automated platforms have improved the diagnostic performance of TPOAb assays. The aim of this study was to evaluate the potential improvement of the inter-method agreement of current automated third generation systems, 12 years after a previous study, which had assessed the analytical variability between semi-automated second generation methods of TPOAb detection.

METHODS

Eight pools of sera from patients with chronic lymphocytic thyroiditis, exhibiting different TPOAb concentrations, were collected from routine laboratory diagnostics and distributed to seven companies throughout Italy. All automated third generation methods were calibrated against the Medical Research Council (MRC) reference preparation 66/387.

RESULTS

The overall mean variability (CV) was 93.6% when results were expressed in part as arbitrary Units (U/mL) and in part as International Units (IU/mL). The conversion of all values in IU/mL resulted in a significant decrease of CV (49.8%). The CV expressed as COM (cut-off concentration multiples) was 64.0%. Agreement of qualitative results was 95.3% with a pronounced difference in the threshold values proposed by manufacturers (range 3.2-35.0 IU/mL).

CONCLUSIONS

These findings confirm the improvement of harmonisation between different methods of automated third generation TPOAb assays. Nevertheless, further efforts should be made in the definition of the positive cut-off concentration to avoid misclassification of AITD patients as well as in a new international reference preparation and in the autoantigen purification modality.