Effect of low-dose selenium on thyroid autoimmunity and thyroid function in UK pregnant women with mild-to-moderate iodine deficiency.

PURPOSE: Selenium is an essential trace mineral and a component of selenoproteins that are involved in the production of thyroid hormones and in regulating the immune response. We aimed to explore the effect of low-dose selenium supplementation on thyroid peroxidase antibody (TPO-Ab) concentration and thyroid function in pregnant women from a mild-to-moderate iodine-deficient population. METHODS: Samples and data were from a secondary analysis of Selenium in PRegnancy INTervention (SPRINT), a double-blind, randomized, placebo-controlled study that recruited 230 women with singleton pregnancies from a UK antenatal clinic at 12 weeks of gestation. Women were randomized to receive 60 µg/day selenium or placebo until delivery. Serum thyroid peroxidase antibodies (TPO-Ab), thyrotropin (TSH) and free thyroxine (FT4) were measured at 12, 20 and 35 weeks and thyroglobulin antibodies (Tg-Ab) at 12 weeks. RESULTS: 93.5% of participants completed the study. Se supplementation had no more effect than placebo in decreasing TPO-Ab concentration or the prevalence of TPO-Ab positivity during the course of pregnancy. In women who were either TPO-Ab or Tg-Ab negative at baseline (Thy-Ab(-ve)), TSH increased and FT4 decreased significantly throughout gestation (P < 0.001), with no difference between treatment groups. In women who were Thy-Ab(+ve) at baseline, TSH tended to decrease and was lower than placebo at 35 weeks (P = 0.050). FT4 fell more on Se than placebo supplementation and was significantly lower at 35 weeks (P = 0.029). CONCLUSIONS: Low-dose selenium supplementation in pregnant women with mild-to-moderate deficiency had no effect on TPO-Ab concentration, but tended to change thyroid function in Thy-Ab(+ve) women.

Highly sensitive cardiac troponin T and long-term mortality in a population of community-derived perimenopausal women: nested case-control study.

OBJECTIVE: To assess the association between baseline levels of highly sensitive cardiac troponin T (hs-cTnT) and long-term mortality in perimenopausal women of the general community using a gender specific 99th percentile reference limit. DESIGN: Nested case control. SETTING: The present study was conducted within the Eindhoven Perimenopausal Osteoporosis Study which is a large prospective cohort of 8503 community-derived women of the city of Eindhoven, The Netherlands. PARTICIPANTS: Cases were defined as Eindhoven Perimenopausal Osteoporosis Study participants who provided an adequate baseline blood sample and subsequently experienced death during follow-up between 1994 and 2003. In total, 123 cases were identified. For each case two matched controls were selected using age, body mass index and hypertension as matching factors. The gender specific 99th percentile reference limit determined in the 246 controls was 8.0 ng/l. MAIN OUTCOME MEASURE: All cause mortality. RESULTS: Hs-cTnT was significantly higher in the cases: 3.0 ng/l versus 2.3 ng/l (p=0.04). After adjustment for matching and clinical risk factors, each 1 SD increase of the level of hs-cTnT was significantly associated with mortality (OR 1.3, 95% CI 1.1 to 1.7, p=0.018). With amino-terminal pro-B-type natriuretic peptide (NT-proBNP) in the multivariable model as a continuous variable the association of hs-cTnT with mortality was lost. With both hs-cTnT and NT-proBNP as dichotomous variables, the gender specific 99th percentile reference limit (8.0 ng/l) was associated with mortality, independent of NT-proBNP (OR 3.7, 95% CI 1.0 to 13.2, p=0.048). CONCLUSIONS: In this study of community-derived perimenopausal women, hs-cTnT was associated with long-term mortality, independent of clinical risk factors. With the use of easily applicable cut-off levels, the gender specific reference limit of hs-cTnT had a prognostic impact that was independent of NT-proBNP.

The new Roche Vitamin D Total assay: fit for its purpose?

BACKGROUND: Measurement of serum 25-hydroxyvitamin D [25(OH)D] is used to assess vitamin D status. We evaluated the analytical performance of a new automated assay, Elecsys Vitamin D Total (Roche Diagnostics, Mannheim, Germany), based on competitive protein binding. METHODS: The Elecsys assay was tested for imprecision, linearity and functional sensitivity at three test-sites and compared to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, a high-performance liquid chromatography (HPLC) method and the Liaison 25(OH) Vitamin D Total immunoassay (Diasorin). RESULTS: Imprecision testing with human serum specimens showed within-run CVs of ≤6% and between-run CVs of ≤8%. The assay was linear from 33 up to at least 111 nmol/L and showed equivalent 25(OH)D levels for matched serum and heparinized plasma samples. The assay correlated reasonable to well with LC-MS/MS (r=0.93; y=1.07x-5.04 nmol/L), HPLC (r=0.91, y=0.90x+3.03 nmol/L) and the Liaison assay (r=0.86, y=1.19x+2.80 nmol/L). Some of the samples showed large between-method differences. CONCLUSIONS: The new Elecsys assay fulfilled present analytical performance requirements and showed close agreement to other well-established methods for 25(OH)D analysis, making it fit for routine assessment of vitamin D status.

The new Roche Vitamin D Total assay: fit for its purpose?

Abstract Background: Measurement of serum 25-hydroxyvitamin D [25(OH)D] is used to assess vitamin D status. We evaluated the analytical performance of a new automated assay, Elecsys Vitamin D Total (Roche Diagnostics, Mannheim, Germany), based on competitive protein binding. Methods: The Elecsys assay was tested for imprecision, linearity and functional sensitivity at three test-sites and compared to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, a high-performance liquid chromatography (HPLC) method and the Liaison 25(OH) Vitamin D Total immunoassay (Diasorin). Results: Imprecision testing with human serum specimens showed within-run CVs of ≤6% and between-run CVs of ≤8%. The assay was linear from 33 up to at least 111 nmol/L and showed equivalent 25(OH)D levels for matched serum and heparinized plasma samples. The assay correlated reasonable to well with LC-MS/MS (r=0.93; y=1.07x-5.04 nmol/L), HPLC (r=0.91, y=0.90x+3.03 nmol/L) and the Liaison assay (r=0.86, y=1.19x+2.80 nmol/L). Some of the samples showed large between-method differences. Conclusions: The new Elecsys assay fulfilled present analytical performance requirements and showed close agreement to other well-established methods for 25(OH)D analysis, making it fit for routine assessment of vitamin D status.

Screening for urinary tract infection with the Sysmex UF-1000i urine flow cytometer.

The diagnosis of urinary tract infection (UTI) by urine culture is time-consuming and can produce up to 60 to 80% negative results. Fast screening methods that can reduce the necessity for urine cultures will have a large impact on overall turnaround time and laboratory economics. We have evaluated the detection of bacteria and leukocytes by a new urine analyzer, the UF-1000i, to identify negative urine samples that can be excluded from urine culture. In total, 1,577 urine samples were analyzed and compared to urine culture. Urine culture showed growth of ≥10(3) CFU/ml in 939 samples (60%). Receiver operating characteristics (ROC) curves and ROC decision plots were been prepared at three different gold standard definitions of a negative urine culture: no growth, growth of bacteria at <10(4) CFU/ml, and growth of bacteria at <10(5) CFU/ml. Also, the reduction in urine cultures and the percentage of false negatives were calculated. At the most stringent gold standard definition of no growth, a chosen sensitivity of 95% resulted in a cutoff value of 26 bacteria/µl, a specificity of 43% and a reduction in urine cultures of only 20%, of which 14% were false negatives. However, at a gold standard definition of <10(5) CFU/ml and a sensitivity of 95%, the UF-1000i cutoff value was 230 bacteria/µl, the specificity was 80%, and the reduction in urine cultures was 52%, of which 0.3% were false negatives. The applicability of the UF-1000i to screen for negative urine samples strongly depends on population characteristics and the definition of a negative urine culture. In our setting, however, the low workload savings and the high percentage of false-negative results do not warrant the UF-1000i to be used as a screening analyzer.

Maternal thyroid function and the outcome of external cephalic version: a prospective cohort study.

BACKGROUND: To investigate the relation between maternal thyroid function and the outcome of external cephalic version (ECV) in breech presentation. METHODS: Prospective cohort study in 141 women (≥ 35 weeks gestation) with a singleton fetus in breech. Blood samples for assessing thyroid function were taken prior to ECV. Main outcome measure was the relation between maternal thyroid function and ECV outcome indicated by post ECV ultrasound. RESULTS: ECV success rate was 77/141 (55%), 41/48 (85%) in multipara and 36/93 (39%) in primipara. Women with a failed ECV attempt had significantly higher TSH concentrations than women with a successful ECV (p < 0.001). Multiple logistic regression showed that TSH (OR: 0.52, 95% CI: 0.30-0.90), nulliparity (OR: 0.11, 95% CI: 0.03-0.36), frank breech (OR: 0.30, 95% CI: 0.10-0.93) and placenta anterior (OR: 0.31, 95% CI: 0.11-0.85) were independently related to ECV success. CONCLUSIONS: Higher TSH levels increase the risk of ECV failure. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT00516555.

Collection of blood specimens by venipuncture for plasma-based coagulation assays: necessity of a discard tube.

The Clinical and Laboratory Standards Institute (CLSI) recently abandoned its recommendation for drawing a discard tube when performing a prothrombin time (PT)/international normalized ratio (INR) or an activated partial thromboplastin time (APTT). Because there is currently no evidence that a discard tube is necessary for more specialized coagulation assays, we studied the need for a discard tube for some of these tests. Blood was obtained from 88 subjects in 2 subsequent citrate tubes. Platelet-free plasma was tested for PT, APTT, antithrombin, protein C, and factors II, V, VIII, IX, and X. Difference and bias between tubes were tested using the Wilcoxon signed rank test and Bland-Altman plots. For only APTT, antithrombin, and protein C was a small, statistically significant mean bias found (0.5 seconds; P = .001; -0.7%, P = .002; and -0.8%, P < .0001, respectively), but the bias of individual samples was not clinically relevant. This was also true for the other parameters tested. The recent CLSI recommendation that a discard tube is not necessary for PT/INR and APTT can be extended to include more specialized plasma-based coagulation assays as identified in this study.

Interlaboratory comparison of the Doumas bilirubin reference method.

OBJECTIVES: To assess the performance of the Doumas bilirubin reference method. DESIGN AND METHODS: Ring trails using pooled patient specimens, a calibrator and human sera enriched with unconjugated bilirubin were analyzed in five laboratories using the Doumas bilirubin reference method. RESULTS: The coefficient of variation for the linear measurement range between laboratories ranged from 1-3%. CONCLUSIONS: The Doumas bilirubin reference method is robust and reproducible. Bilirubin results using this method may be used in the development of more accurate and reliable calibrators.

Maternal thyroid hormone concentration during late gestation is associated with foetal position at birth.

OBJECTIVE: To evaluate whether there is an association between maternal thyroid hormone and foetal cephalic head position at term gestation. CONTEXT: Rotation and flexion of the head enables the foetus to negotiate the birth canal. Low-normal range thyroid hormone concentrations in euthyroid pregnant women constitute a risk of infant motor abnormality. We hypothesized that low normal maternal thyroid hormone levels are associated with increased risk of abnormal foetal position at delivery. DESIGN: In 960 healthy Dutch women with term gestation and cephalic foetal presentation, thyroid parameters [foetal T4 (FT4), TSH and thyroid peroxidase antibody] were assessed at 36 weeks of gestation, and related to foetal head position (anterior cephalic vs. abnormal cephalic) and delivery mode (spontaneous vs. assisted delivery). RESULTS: Women presenting in anterior position (n = 891) had significantly higher FT4 levels at 36 weeks of gestation than those with abnormal cephalic presentation (n = 69). There were no between-group differences for TSH. Regression analyses indicated that the risk of abnormal head position decreased as a function of increasing FT4 [single odds ratio (OR) = 0.87, 95% confidence intervals (CI) 0.77-0.98; multivariate OR = 0.88, 95% CI 0.72-0.99)]. A similar inverse relationship between maternal FT4 and risk of assisted delivery was obtained (OR = 0.86, 95% CI 0.79-0.95; OR = 0.91, 95% CI 0.84-0.98). CONCLUSION: The lower the maternal FT4 concentration at 36 weeks of gestation, the higher the risk of abnormal cephalic foetal presentation and assisted delivery.

The effect of paraproteins on the erythrocyte sedimentation rate: a comparison between the StarrSed and TEST 1.

BACKGROUND: The principle of the erythrocyte sedimentation rate (ESR) as assessed by TEST 1 is different from that of Westergren-based methods. This could result in different influences on the tests by paraproteins. METHODS: We investigated the effect of paraproteins on ESR readings by TEST 1 (y) and the StarrSed (x), a Westergren-based method, in 142 patients with paraproteinaemia. Agreement (Passing-Bablok) and bias (Bland-Altman) between methods was investigated and compared with that of a control population. RESULTS: A poor agreement between the two methods was found in patients with a paraprotein (y = 0.67x + 3.3) in comparison with that of the control population (y = 0.96x + 0.2). Large differences between methods were present when ESR readings were >40 mm/hour, but clinical interpretation was similar in 90% of cases. Linear regression showed a concentration dependent influence of paraproteins on ESR readings by the StarrSed, especially for immunoglobulin class IgM. CONCLUSION: ESR readings by TEST 1 result in similar clinical interpretation for most subjects, but readings are less influenced by the presence of a paraprotein than those of a Westergren-based method.

An improved laboratory protocol to assess subarachnoid haemorrhage in patients with negative cranial CT scan.

BACKGROUND: The laboratory analysis of cerebrospinal fluid (CSF) plays a key role in considering subarachnoid haemorrhage (SAH) in patients with clinical suspicion, but negative CT scan. Although the determination of the CSF bilirubin concentration generally provides high sensitivity, it was recently shown that specificity and positive predictive value are unacceptably low, limiting its use as a diagnostic tool. METHODS: We intended to design and evaluate an improved laboratory protocol, which fulfills the requirement of better specificity without losing sensitivity. We present a procedure in which a "bili-excess" concentration is determined, which is the surplus CSF bilirubin measured after subtraction of an estimated upper limit for the individual patient. The latter is calculated from [bilirubin](serum), [albumin](serum) and [albumin](CSF), taking into account the propagation of analytical errors in the individual analyses. We investigated the applicability of direct absorption vs. derivative spectroscopy, thereby addressing the influence of various calibration methods. We evaluated our procedure in 92 CSF samples drawn from patients with (n=37) and without (n=55) clinical suspicion of SAH. RESULTS: In our study population, we show that specificity increases from 0.83 (95% CI, 0.74-0.91) to 1.00 (95% CI, 0.96-1.00) using the bili-excess concept, with an established upper limit for bili-excess of 0.11 micromol/L instead of the recommended use of an "uncorrected" CSF bilirubin upper limit of 0.20 micromol/L. Sensitivity in both cases is 1.00 (95% CI, 0.66-1.00). We demonstrate the merit of allowing for analytical imprecision in the bili-excess concept. CONCLUSIONS: We provide a quantitative procedure to explore the likelihood of (CT-negative) SAH independent of the absolute CSF bilirubin concentration by considering the "bili-excess" concentration per individual, using derivative spectroscopy to determine CSF bilirubin. This procedure led to an increase in specificity to 1.00 (95% CI, 0.96-1.00) in our study population.

The relation between gestational thyroid parameters and depression: a reflection of the downregulation of the immune system during pregnancy?

OBJECTIVE: To assess the relation between thyroid parameters and an episode of major depression at different trimesters during pregnancy, taking into account possible confounders. DESIGN: Prospective follow-up of 1017 pregnant women from the general population with assessment of thyroid parameters and depression using syndromal diagnosis interviews at 12, 24, and 36 weeks' gestation. MAIN OUTCOME: The prevalence of major depression decreased from 5.3% to 2.9%, and that of elevated concentrations of thyroid peroxidase antibody (TPOAb) titers from 8.4% to 6.5% toward the end of term. Subclinical hyperthyroidism not related to TPO-Ab (odds ration [OR] 3.6; 95% confidence interval [CI]: 1.2-0.2) and TPO-Ab (OR 2.1; 95% CI: 1.1-5.8) at 12 weeks' gestation, and TPO-Ab (OR 2.8; 95% CI 1.9-7.1) at 24 weeks' gestation were independently related to major depression. Anxiety and the occurrence of stressful life events were related to depression at all trimesters. CONCLUSIONS: The occurrence of major depression and high titers of TPO-Ab show a similar pattern of decline throughout pregnancy. During early gestation, thyroid autoimmunity seems to be related to depression while at the end of term-when there is maximal downregulation of the immune system-autoimmunity does not seem to play an important role with regard to the occurrence of depression.

Do we measure bilirubin correctly anno 2005?

We observed 30% discrepancy between liquid chemistry and dry chemistry analysers for the determination of total bilirubin in human adult serum samples, which were consistent with a 20% overestimation and 10% underestimation relative to a Jendrassik-Grof reference method, respectively. In contrast, standard reference material SRM916, which was recently recommended as being the most suitable material for attaining interlaboratory agreement, shows very good agreement on both types of analysers, as well as close to 100% recovery with respect to the reference method. We show that the liquid vs. dry bilirubin discrepancies seem to originate in the presence of either conjugated or delta-bilirubin. Our observations make it clear that good interlaboratory (or inter-analyser) agreement between bilirubin reference materials does not guarantee the same for bilirubin concentrations in human serum samples.

A quantitative appraisal of interference by icodextrin metabolites in point-of-care glucose analyses.

An important number of patients dependent on renal dialysis prefer peritoneal dialysis to hemodialysis. In the case of peritoneal dialysis, the glucose polymer icodextrin is frequently added to the dialysis fluid as an osmotic agent, since this polymer is able to maintain an osmotic gradient across the peritoneal membrane longer than monomeric glucose, leading to a prolonged effective ultrafiltration time. It was previously shown that icodextrin is partly able to enter the blood via the lymphatic system, where hydrolysis to glucose oligomers such as maltose and maltotriose occurs. The presence of these oligomers in the blood appears to cause significant overestimations of the glucose values in several point-of-care (POC) glucose analyzers, with potentially dramatic consequences. This effect has been investigated for a series of POC glucose analyzers, both by analyzing the blood of peritoneal dialysis patients and by an in vitro investigation of the quantitative effects of maltose and maltotriose. In particular, POC analyzers utilizing the bacterially produced enzyme glucose dehydrogenase seem to lack glucose specificity.

Multicenter evaluation of the commutability of a potential reference material for harmonization of enzyme activities.

Standardization of laboratory results allows for the use of common reference intervals and can be achieved via calibration of field methods with secondary reference materials. These harmonization materials should be commutable, i.e., they produce identical numerical results independent of assay principle or platform. This study assessed the commutability of a cryolyoprotectant-containing harmonization material, obtained from the Dutch Foundation for Quality Assessment in Clinical Laboratories, that is intended to harmonize measurements of enzyme activities within the Dutch project "Calibration 2000". The catalytic concentrations of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, gamma-glutamyltransferase and creatine kinase were analyzed in pooled patient sera and in the reference material in 14 laboratories. On liquid chemistry analyzers the harmonization material behaves like patient material. The enzyme activities measured in it fall on the regression lines calculated from activities measured in serum samples. For dry chemistry analyzers the activities of all enzymes measured in the harmonizator differ from the serum-based regression line. We show that this is due to the sucrose-containing cryolyoprotectant in the harmonization material. For each enzyme, correction factors were calculated that compensated for the bias and proved to be constant between reagent lots. Depending on the enzyme activity measured, application of these factors leads to 2- to 10-fold reduction of between-laboratory percentage coefficient of variation. Thus, additives to (potential) reference materials may alter their matrix in a way that interferes with analysis on certain test systems. The bias caused may be quantifiable and correctable. Establishment of correction factors leads to analytical uncertainties and costs. Therefore, matrix-based materials without additives should be selected as reference materials.

Low concentrations of maternal thyroxin during early gestation: a risk factor of breech presentation?

OBJECTIVE: To evaluate the relation between breech position at term (>37 weeks of gestation) and low maternal fT4 levels during gestation in women not suffering from overt thyroid dysfunction. DESIGN: A prospective cohort study of pregnant women. SETTING: Community-based study. POPULATION/SAMPLE: At random selected pregnant women of the general population. METHODS: At antenatal booking, based on thyroid function assessed at 12 weeks of gestation in a large cohort of pregnant women, two groups of participants were defined: women with low fT4 levels-below the 10th centile (n= 135) and women with fT4-between the 50th and 90th centiles at 12 weeks of gestation (n= 135). Women with clinical thyroid dysfunction (fT4 and TSH outside reference range) at 12 weeks of gestation were excluded. Maternal thyroid function (fT4 and TSH) was subsequently assessed at 24 and 32 weeks of gestation. Analysis refers to 204 women who met the inclusion and exclusion criteria and in whom all thyroid parameters were assessed. MAIN OUTCOME MEASURES: Fetal presentation (cephalic-breech) at delivery in women with term gestation (>37 weeks of gestation) in relation to maternal thyroid function at 12, 24 and 34 weeks of gestation. RESULTS: Breech presentation at term delivery was independently related to fT4 levels <10th centile at 12 weeks of gestation (OR = 4.7, 95% CI 1.1-19 [but not to an fT4 level below the 10th centile at 24 and 32 weeks of gestation]) as well as primiparity (OR = 4.7, 95% CI 1.3-15). CONCLUSIONS: Women with hypothyroxinaemia (fT4 level at the lowest 10th centile) during early gestation but without overt thyroid function are at risk for fetal breech presentation at term (>37 weeks of gestation).