Factitiously Elevated Total Triiodothyronine in a Euthyroid Patient with Multiple Myeloma

Sporadic reports of factitious elevations of thyroid hormones related to laboratory interference from autoantibodies and multiple myeloma paraproteins have appeared in the literature. Such clinically confusing laboratory results can lead to erroneous diagnoses and inappropriate treatments. We report an additional case of a patient with multiple myeloma and an IgG paraproteinemia who had such a spurious elevation of total T3 complicating her levothyroxine management of hypothyroidism. In addition, we alert clinicians that differences in performance characteristics between various manufacturers' test platforms may also cause spurious reports.

The Prevalence of Euthyroid Hypertriiodothyroninemia in Newly Diagnosed Multiple Myeloma and its Clinical Characteristics

OBJECTIVE

To evaluate the prevalence of euthyroid hypertriiodothyroninemia and/or hyperthyroxinemia and its clinical characteristics in multiple myeloma (MM) patients.

METHODS

Previously untreated, newly diagnosed patients with MM were enrolled at the Beijing Chao-yang Hospital between January 2016 and December 2019. Thyroid function and clinical characteristics were analyzed.

RESULTS

A total of 105 patients were enrolled in this study. Thirteen (12.38%) patients exhibited euthyroid hypertriiodothyroninemia with strikingly elevated total triiodothyronine (TT3) levels (>8 ng/mL). Among these 13 patients, 12 patients were immunoglobulin (Ig) G type (92.31%), and 1 patient was light-chain κ type (7.69%). Compared with other patients with MM, patients with hypertriiodothyroninemia were more likely to be IgG type and had higher serum globulin and lower albumin levels and more advanced International Staging System stage (all P < .05). Among the 13 euthyroid hypertriiodothyroninemia patients, 8 patients have been followed up and checked for thyroid function. The TT3 levels in all 8 patients were normalized to the reference range after antimyeloma chemotherapy.

CONCLUSION

About 12% of patients with MM had euthyroid hypertriiodothyroninemia. Their strikingly elevated TT3 was normalized after chemotherapy. Clinicians should be aware of the possibility of high TT3 levels in euthyroid patients with MM and the potential risk of MM in patients with strikingly elevated TT3.

Falsely Elevated Thyroid-Stimulating Hormone Results due to Interference by M-Component of IgG-Lambda Type

Heterophilic antibodies but also M-components can interfere with laboratory tests causing erroneous results. We report the case of a 75-year-old man with myeloma and a monoclonal immunoglobulin component (M-component) that caused elevated thyroid-stimulating hormone (TSH) results. The M-component was of the IgG-lambda type. Thyroid markers were analyzed repeatedly, and there was a clear association between IgG concentrations and TSH values (R² = 0.724). The highest TSH value was 75 mIU/L. Polyethylene glycol (PEG) precipitation of intact immunoglobulins was used to investigate if there was an antibody-related interference problem. The PEG treatment normalized the TSH value, showing that the cause of the elevated TSH result was due to interference caused by the M-component. In conclusion, it is important to remember that both heterophilic antibodies and M-components may cause erroneous results.

Is It T3 Thyrotoxicosis? A Case of Falsely Elevated Tri-Iodothyronine (T3) Levels Leading to a Diagnosis of Multiple Myeloma

We are presenting a case of falsely elevated T3 levels in a patient due to interference from monoclonal immunoglobulins. A 56-year-old, clinically euthyroid man referred to the endocrinology clinic of the Aga Khan university, Karachi Pakistan, for possible T3 thyrotoxicosis after thyroid function tests revealed total T3 >12.32 nmol/L (reference range 0.6–2.79), normal TSH, and total T4 level. There was a mismatch in clinical and laboratory parameters and preliminary laboratory results were suggestive of thyroid binding globulin abnormalities. Further evaluation in this context unmasked multiple myeloma. The presence of monoclonal immunoglobulins can lead to assay interference and spurious results. To the best of our knowledge, this is the second case defining the cause of falsely elevated T3 levels, due to assay interferences with binding of T3 only to monoclonal immunoglobulins.

Pseudohyperthyroxinemia in a hypothyroid patient secondary to chronic phlegmon

Background: Elevated free thyroxine could be primary or secondary, endogenous or exogenous and often presents with symptoms of hyperthyroidism. Thyroxine levels are low in hypothyroidism, where the individual requires exogenous supplementation to maintain a euthyroid state. However, thyroxine levels may be elevated in a hypothyroid patient because of over-supplementation/over-suppression with exogenous agent(s) or secondary to other pathologies and rarely, laboratory error or assay interference may cause alteration in the levels of the thyroid hormones.

Case report: A 44-year-old man with well controlled hypothyroidism was referred for assessment of markedly elevated TSH and free thyroxine levels with low free T3. Clinically the patient was hypothyroid with symptoms of fatigue and weight gain of 30 pounds over the past 3-months and the TSH levels were consistent with marked hypothyroidism. However, free thyrxoine was markedly elevated, opposite of what to be expected. A systematic evaluation, presented here, was helpful in the diagnosis of pseudohyperthyroxinemia secondary to assay interferences in a timely fashion, avoiding unnecessary further investigations.

Conclusions: Interference in immunoassays is an important clinical problem that is underestimated and can have important clinical consequences. It is important to recognize the possibility of such interferences early in the diagnostic process and to implement protocols to identify these whenever possible, in a timely fashion, to prevent untoward consequences. Vigilance by both the clinician and the laboratory staff is important.

Spurious t3 thyrotoxicosis unmasking multiple myeloma

Objective. To document a case of spurious T3 thyrotoxicosis in a 54-year-old woman. Methods. We present the diagnostic approach of a patient with euthyroid hypertri-iodothyronemia. Results. A 54-year-old, clinically euthyroid woman without personal or family history of thyroid disease referred to endocrinology for possible T3 thyrotoxicosis, after thyroid function tests revealed total T3 > 800 ng/dL (reference range 60-181), normal TSH, and T4. The laboratory data were not compatible with the clinical picture, so thyroid binding globulin abnormalities were suspected. Additional laboratory studies confirmed the diagnosis of multiple myeloma. Conclusion. Monoclonal gammopathy is characterized by the presence of a monoclonal immunoglobulin in the serum or urine, occurring in multiple myeloma, and can cause assay interference and spurious results. We identify a newly recognized cause of euthyroid hypertri-iodothyronemia, due to binding of T3 to monoclonal immunoglobulins in the setting of multiple myeloma. Our case is the only one to date suggesting that monoclonal immunoglobulins from multiple myeloma may exhibit binding to T3 only.

How paraproteins can affect laboratory assays: spurious results and biological effects

The presence of large amounts of monoclonal paraprotein in the serum can lead to a range of spurious laboratory results. These may result from analytical interference of the M-protein through chemical or immunological means, or from pre-analytical interference; the different modes of interference are explored in this review along with suggested methods of prevention or detection.

Interference in thyroid-stimulating hormone determination

BACKGROUND

Thyroid-stimulating hormone (TSH) measurement plays a major role in the diagnosis of thyroid disorders. Despite the good quality of immunochemical tests measuring TSH levels, the presence of interfering substances can sometimes alter the TSH results.

DESIGN

We reported the case of a 79-year-old man affected by primary autoimmune hypothyroidism hospitalized for pneumonia. A TSH value > 100 mIU L(-1) (reference: 0.44 mIU L(-1)) was found at admission. No signs and symptoms of hypothyroidism were found upon clinical examination and serum concentration of the free thyroxine (FT4) was normal.

RESULTS

Serum treatment in heterophile antibody blocking tubes did not change the TSH result in our assay, while normal levels were found in a different immunoassay method. An abnormal pattern was found in protein electrophoresis at admission, with IgG / j and IgM / k monoclonal bands proved in immunofixation. Interestingly, the disappearance of monoclonal bands was paralleled with a normalization of the TSH value.

CONCLUSIONS

We suggest in this study that the TSH determination might be influenced by the presence of transient paraproteins.

Protein precipitation as a possible important pitfall in the clinical chemistry analysis of blood samples containing monoclonal immunoglobulins: 2 case reports and a review of the literature

Two case reports are presented, both illustrating an analytical interference caused by monoclonal immunoglobulins. Falsely low results were obtained in the routine analysis of glucose, CRP and HDL-cholesterol. When analysing samples containing paraproteins, various problems can be encountered in the clinical laboratory: next to the antibody effect, pseudohyponatraemia, hyperviscosity, cryoglobulinaemia and gel formation have to be taken into account. In our two cases the interference was caused by paraprotein precipitation, causing an increased turbidity and an apparent increase of light absorbance at every wavelength due to light scattering, including the wavelengths used in the clinical chemistry assays. We review the literature on this sometimes overlooked interference in photometric/turbidimetric assays. This reaction is based on the insolubility of these proteins in specific physico-chemical circumstances in which many variables are involved, among others: pH and ionic strength, presence of preservatives and surfactants in the assays, pI and other specific properties of the monoclonal immunoglobulins. The complexity of the problem makes predicting or preventing this probably infrequent interference usually impossible. This artifact can cause both false positive and false negative results in multiple parameters (e.g. bilirubin, creatinine, iron, urea, uric acid), the most frequently reported analyte being phosphate. The Sia water test (Sia euglobulin precipitation test) can provide a first clue to a paraprotein aggregation; confirmation can be obtained by observing the time/ absorbance curves of the analysis, performing the test manually or setting up a serial dilution of the sample. The problem can be solved by avoiding the presence of the proteins in the assay, performing the analysis using an alternative method or diluting out the interference. Both laboratorians and clinicians should be aware of interferences in the clinical laboratory since the clinical consequences could be important.