Variability of Thyroid Measurements from Ultrasound and Laboratory in a Repeated Measurements Study

Semiautomated Software to Improve Stability and Reduce Operator-Induced Variation in Vascular Ultrasound Speckle Tracking

OBJECTIVES

Ultrasound is useful in predicting arteriovenous fistula (AVF) maturation, which is essential for hemodialysis in end-stage renal disease patients. We developed ultrasound software that measures circumferential vessel wall strain (distensibility) using conventional ultrasound Digital Imaging and Communications in Medicine (DICOM) data. We evaluated user-induced variability in measurement of arterial wall distensibility and upon finding considerable variation we developed and tested 2 methods for semiautomated measurement.

METHODS

Ultrasound scanning of arteries of 10 subjects scheduled for AVF surgery were performed. The top and bottom of the vessel wall were tracked using the Kanade-Lucas-Tomasi (KLT) feature-tracking algorithm over the stack of images in the DICOM cine loops. The wall distensibility was calculated from the change of vessel diameter over time. Two semiautomated methods were used for comparison.

RESULTS

The location of points selected by users for the cine loops varied significantly, with a maximum spread of up to 120 pixels (7.8 mm) for the top and up to 140 pixels (9.1 mm) for the bottom of the vessel wall. This variation in users' point selection contributed to the variation in distensibility measurements (ranging from 5.63 to 41.04%). Both semiautomated methods substantially reduced variation and were highly correlated with the median distensibility values obtained by the 10 users.

CONCLUSIONS

Minimizing user-induced variation by standardizing point selection will increase reproducibility and reliability of distensibility measurements. Our recent semiautomated software may help expand use in clinical studies to better understand the role of vascular wall compliance in predicting the maturation of fistulas.

Interpretation of TSH and T4 for diagnosing minor alterations in thyroid function: a comparative analysis of two separate longitudinal cohorts

Background

Minor alterations in thyroid function are frequent, and interpretation of thyroid function tests in the individual patient can be challenging. Furthermore, the choice of thyroid function test is debatable. To inform the debate, we performed a comparative evaluation of the variation in thyrotropin (TSH) and thyroxine (T4) in two different cohorts to illustrate the precision of TSH and T4 in the diagnosis and monitoring of thyroid dysfunction.

Methods

A comparative analysis of two separate longitudinal studies previously surveyed with monthly blood sampling for one year among 35 subjects. Participants were included based on T4 within the reference range and TSH either within (euthyroid; n = 15) or above (subclinical hypothyroidism; n = 20) the laboratory reference range on two independent blood samplings before inclusion. Exclusion criteria were known thyroid disease or use of thyroid interfering medication. TSH and T4 in individual samples were measured in a single batch to prevent between-batch variation. The distributions TSH and T4 were compared among euthyroid and subclinical hypothyroid individuals, and bootstrap estimates were used to calculate area under the curve (AUC).

Results

Collection of twelve, monthly blood samples in the 35 participants provided 420 samples, and data completeness was 100%. The mean TSH was 1.27/7.19 mIU/L and the mean total T4 was 106/85 nmol/L in euthyroid/subclinical hypothyroid participants. The subclinical hypothyroidism state deviated from the euthyroid by 20% for total T4 and by 466% for TSH. The overlap between the euthyroid and subclinical hypothyroid groups was 92.6% (389/420) for total T4 and 9.0% (38/420) of test results for TSH. The estimated AUC was 0.999 (95%-CI: 0.995; 1.00) for TSH and 0.853 (0.736; 0.935) for total T4. There was no confidence interval overlap between participant groups for TSH while there was a considerable overlap for total T4 (p < 0.001).

Conclusion

The distributions of thyroid function tests illustrated how TSH outperforms T4 for detecting delicate differences in thyroid function in an individual. Thus, TSH was markedly better than T4 to discriminate between the subtle differences in thyroid function corroborating that TSH is the more sensitive and accurate index of thyroid function status in the individual patient.

Prior iodine exposure and impact on thyroid function during controlled ovarian hyperstimulation: A prospective study

AIMS

Iodine supplements are recommended for women planning pregnancy, but their impact on thyroid function during controlled ovarian hyperstimulation (COH) and into pregnancy is unknown. The aim of this study was to assess the impact of iodine supplementation on thyroid function during COH.

METHODS

One-hundred and six euthyroid women (thyroid stimulating hormone (TSH) 0.4-2.5 mIU/L) planning their first COH cycle were subdivided according to iodine supplementation (nil, <6 months, ≥6 months) and compared to levothyroxine (LT4)-treated controls. Serial TSH, free thyroxine, free triiodothyronine and thyroglobulin (Tg) levels were recorded at four time points: (i) baseline, (ii) day 7 ovarian stimulation, (iii) ovulation trigger and (iv) two weeks post oocyte retrieval. Oocyte numbers, fertilisation rates and pregnancy outcome were recorded.

RESULTS

TSH increased during COH for those women taking iodine supplements for ≥6 months (P = 0.025). One quarter recorded a TSH level >2.5 mIU/L before embryo transfer. A similar increase in TSH was demonstrated by LT4-dependent controls (P = 0.024) but not the remaining subgroups. Tg levels did not change during COH in any group but decreased significantly post oocyte retrieval if nil iodine (P < 0.0001) or supplemented for ≥6 months (P < 0.005). Iodine supplementation did not influence oocyte count, fertilisation or implantation rates. Women taking iodine for <6 months were four times more likely to achieve a live birth than women taking iodine for longer.

CONCLUSIONS

Women taking iodine supplements for ≥6 months are less able to adapt to the thyroidal demands of COH, with responses comparable to LT4-dependent patients.