Autoantibody profiling of patients with autoimmune thyroid disease using a new multiplexed immunoassay method

Clinical practice guidelines for the management of hypothyroidism

INTRODUCTION

Hypothyroidism has long been known for its effects on different organ systems, leading to hypometabolism. However, subclinical hypothyroidism, its most prevalent form, has been recently related to cardiovascular risk and also to maternal-fetal complications in pregnant women.

OBJECTIVES

In these clinical practice guidelines, several aspects of this field have been discussed with the clear objectives of helping physicians treat patients with hypothyroidism, and of sharing some of our Latin American-based clinical experience.

MATERIALS AND METHODS

The Latin American Thyroid Society commissioned a Task Force on Hypothyroidism to develop evidence-based clinical guidelines on hypothyroidism. A systematic review of the available literature, focused on the primary databases of MedLine/PubMed and Lilacs/SciELO was performed. Filters to assess methodological quality were applied to select the best quality studies. The strength of recommendation on a scale from A-D was based on the Oxford Centre for Evidence--based Medicine, Levels of Evidence 2009, allowing an unbiased opinion devoid of subjective viewpoints. The areas of interest for the studies comprised diagnosis, screening, treatment and a special section for hypothyroidism in pregnancy.

RESULTS

Several questions based on diagnosis, screening, treatment of hypothyroidism in adult population and specifically in pregnant women were posed. Twenty six recommendations were created based on the answers to these questions. Despite the fact that evidence in some areas of hypothyroidism, such as therapy, is lacking, out of 279 references, 73% were Grade A and B, 8% Grade C and 19% Grade D.

CONCLUSIONS

These evidence-based clinical guidelines on hypothyroidism will provide unified criteria for management of hypothyroidism throughout Latin America. Although most of the studies referred to are from all over the world, the point of view of thyroidologists from Latin America is also given.

Current state of diagnostic technologies in the autoimmunology laboratory

The methods for detecting and measuring autoantibodies have evolved markedly in recent years, encompassing three generations of analytical technologies. Many different immunoassay methods have been developed and used for research and laboratory practice purposes, from the early conventional (or monoplex) analytical methods able to detect single autoantibodies to the more recent multiplex platforms that can quantify tens of molecules. Although it has been in use for over 50 years, indirect immunofluorescence remains the standard method for research on many types of autoantibodies, due to its characteristics of diagnostic sensitivity and also to recent technological innovations which permit it a greater level of automation and standardization. The recent multiplex immunometric methods, with varying levels of automation, present characteristics of higher diagnostic accuracy, but are not yet widely diffused in autoimmunology laboratories due to the limited number of autoantibodies that are detectable, and due to the high cost of reagents and systems. Technological advancement in autoimmunology continues to evolve rapidly, and in the coming years new proteomic techniques will be able to radically change the approach to diagnostics and possibly also clinical treatment of autoimmune diseases. The scope of this review is to update the state of the art of technologies and methods for the measurement of autoantibodies, with special reference to innovations in indirect immunofluorescence and in multiple proteomic methods.

Definition of reference limits for autoantibodies to thyroid peroxidase and thyroglobulin in a large population of outpatients using an indirect method based on current data

CONTEXT

The reference limits for thyroid antibodies are generally made by measuring thyroid peroxidase and thyroglobulin antibody values in a group of healthy subjects (direct method), as proposed by the National Academy of Clinical Biochemistry.

OBJECTIVE

To define the upper reference limits of thyroid peroxidase and thyroglobulin, by using an indirect method to analyze data from a large number of outpatients that were stored in the information system of a general hospital laboratory.

DESIGN

Thyroid peroxidase and thyroglobulin values from 21 492 patients, who had undergone antithyroid antibody measurements, were retrieved from the laboratory information system; the upper reference limits (in the top 97.5 percentile) were calculated using the indirect Kairisto method, after exclusion of outliers.

RESULTS

The mean upper reference limits for females and males were 15 kIU/L and 9 kIU/L for thyroid peroxidase, and 21 kIU/L and 19 kIU/L for thyroglobulin, respectively. The upper limits showed minimal or no differences in the different age classes in either females or males.

CONCLUSIONS

Using a vast population of patients, we demonstrated that the upper limits for thyroid antibodies are much lower than the values obtained with classic, direct methods and that they do not vary in relation to age and sex.

The diagnostic role of autoantibodies in the prediction of organ-specific autoimmune diseases

Due to their pathogenetic role, many serum autoantibodies can be detected a long time before the clinical onset and during the course of organ-specific autoimmune diseases. For these reasons, autoantibodies can be used as predictive markers of an ongoing disease (in healthy subjects) and of disease activity and severity (in ill patients). The new multiplex diagnostic technologies introduced recently in laboratory medicine allow the simultaneous detection of several different autoantibodies and can be used for screening purposes in open populations or high-risk groups. This review examines the various autoantibodies of demonstrated predictive role in organ-specific autoimmune diseases and it introduces the state-of-the-art in the detection of multiple autoantibodies with proteomic systems.

The CD40, CTLA-4, thyroglobulin, TSH receptor, and PTPN22 gene quintet and its contribution to thyroid autoimmunity: back to the future

Autoimmune thyroid diseases (AITD) are common autoimmune diseases, affecting up to 5% of the general population. Thyroid-directed autoimmunity is manifested in two classical autoimmune conditions, Hashimoto's thyroiditis, resulting in hypothyroidism and Graves' disease resulting in hyperthyroidism. Autoimmune thyroid diseases arise due to an interplay between environmental and genetic factors. In the past decade significant progress has been made in our understanding of the genetic contribution to the etiology of AITD. Indeed, several AITD susceptibility genes have been identified. Some of these susceptibility genes are specific to either Graves' disease or Hashimoto's thyroiditis, while others confer susceptibility to both conditions. Both immunoregulatory genes and thyroid specific genes contribute to the pathogenesis of AITD. The time is now ripe to examine the mechanistic basis for the contribution of genetic factors to the etiology of AITD. In this review, we will focus on the contribution of non-MHC II genes.

Autoimmune thyroid diseases

PURPOSE OF REVIEW

Interesting clinical and basic studies have been published in the field of autoimmune thyroiditis (represented by Graves' disease and Hashimoto's thyroiditis) since January 2005. The review is organized into four main areas: genetics, environment, adaptive immune system, and innate immune system.

RECENT FINDINGS

The quest continues for the identification of susceptibility genes for autoimmune thyroiditis. In addition to the classical major histocompatibility complex class II genes and cytotoxic T cell antigen-4, new studies have appeared on CD40 the protein tyrosine phosphatase-22. Too much iodine increases the incidence of Hashimoto's thyroiditis, perhaps by augmenting the antigenicity of thyroglobulin. T regulatory cells, Toll-like receptors and presentation of lipid antigens by CD1 molecules are new areas of basic immunological investigation that have been applied to autoimmune thyroiditis.

SUMMARY

Overall, the studies have greatly expanded our understanding of the pathogenesis of thyroiditis. They have opened new lines of investigations that will ultimately result in a better clinical practice.