Application of a new AMIQAS computer program for integrated quality control, method evaluation and proficiency testing

Long Term Effects on Risk Factors for Cardiovascular Disease after 12-Months of Aerobic Exercise Intervention - A Worksite RCT among Cleaners

Objectives

Occupational groups exposed to high occupational physical activity have an increased risk for cardiovascular disease (CVD). This may be explained by the high relative aerobic workload. Enhanced cardiorespiratory fitness reduces the relative aerobic workload. Thus, the aim was to evaluate the 12-months effects of worksite aerobic exercise on risk factors for CVD among cleaners.

Methods

One hundred and sixteen cleaners aged 18–65 years were randomized to a group performing aerobic exercise and a reference group receiving lectures. Outcomes were collected at baseline and after 12-months. A repeated measures 2×2 multi-adjusted mixed-model design was applied to compare the between-group differences using intention-to-treat analysis.

Results

Between-group differences (p<0.05) were found favouring the aerobic exercise group: cardiorespiratory fitness 2.15 (SE 1.03) mlO₂/min/kg, aerobic workload -2.15 (SE 1.06) %HRR, resting HR -5.31 (SE 1.61) beats/min, high sensitive C-reactive protein -0.65 (SE 0.24) μg/ml. The blood pressure was unaltered. Stratified analyses on relative aerobic workload at baseline revealed that those with relative aerobic workloads ≥30% of HRR seems to impose a notable adverse effect on resting and ambulatory blood pressure.

Conclusion

This long-term worksite aerobic exercise intervention among cleaners led to several beneficial effects, but also potential adverse effects among those with high relative aerobic workloads.

Trial Registration

Controlled-Trials.com ISRCTN86682076

Aerobic exercise reduces biomarkers related to cardiovascular risk among cleaners: effects of a worksite intervention RCT

Purpose

Blue-collar workers have an increased risk of cardiovascular disease. Accordingly, elevated levels of biomarkers related to risk of cardiovascular disease, such as high-sensitive C-reactive protein, have been observed among blue-collar workers. The objective was to examine whether an aerobic exercise worksite intervention changes the level of inflammation biomarkers among cleaners.

Methods

The design was a cluster-randomized controlled trial with 4-month worksite intervention. Before the 116 cleaners aged 18–65 years were randomized, they signed an informed consent form. The reference group (n = 59) received lectures, and the aerobic exercise group (n = 57) performed worksite aerobic exercise (30 min twice a week). Levels of biomarkers (high-sensitive C-reactive protein, fibrinogen, cholesterol, low- and high-density lipoprotein cholesterol and triglyceride) were collected at baseline and after 4 months. A repeated-measure, multi-adjusted, mixed-model intention-to-treat analysis was applied to compare between-group differences. The study was registered as ISRCTN86682076.

Results

Significant (p < 0.05) between-group reductions from baseline to follow-up were found for high-sensitive C-reactive protein (−0.54 ± 0.20 µg/ml; 95 % CI −0.94, −0.14), low-density lipoprotein cholesterol (−0.32 ± 0.11 mmol/L; 95 % CI −0.54, −0.10) and the ratios of LDL/HDL (−0.30 ± 0.08; 95 % CI −0.46, −0.14), and LDL/TC cholesterol (−0.04 ± 0.02; 95 % CI −0.07, −0.01).

Conclusion

This study indicates that an aerobic exercise intervention among cleaners leads to reduced levels of high-sensitive C-reactive protein and low-density lipoprotein cholesterol, and an unaltered level of fibrinogen. The aerobic exercise seems to improve inflammatory levels and lipoprotein profile among cleaners, with no signs of cardiovascular overload.

Associations of subjective vitality with DNA damage, cardiovascular risk factors and physical performance

AIM

To examine associations of DNA damage, cardiovascular risk factors and physical performance with vitality, in middle-aged men. We also sought to elucidate underlying factors of physical performance by comparing physical performance parameters to DNA damage parameters and cardiovascular risk factors.

METHODS

We studied 2487 participants from the Metropolit cohort of 11 532 men born in 1953 in the Copenhagen Metropolitan area. The vitality level was estimated using the SF-36 vitality scale. Cardiovascular risk factors were determined by body mass index (BMI), and haematological biochemistry tests obtained from non-fasting participants. DNA damage parameters were measured in peripheral blood mononuclear cells (PBMCs) from as many participants as possible from a representative subset of 207 participants.

RESULTS

Vitality was inversely associated with spontaneous DNA breaks (measured by comet assay) (P = 0.046) and BMI (P = 0.002), and positively associated with all of the physical performance parameters (all P < 0.001). Also, we found several associations between physical performance parameters and cardiovascular risk factors. In addition, the load of short telomeres was inversely associated with maximum jump force (P = 0.018), with lowered significance after exclusion of either arthritis sufferers (P = 0.035) or smokers (P = 0.031).

CONCLUSION

Here, we show that self-reported vitality is associated with DNA breaks, BMI and objective (measured) physical performance in a cohort of middle-aged men. Several other associations in this study verify clinical observations in medical practice. In addition, the load of short telomeres may be linked to peak performance in certain musculoskeletal activities.

Social gradient in allostatic load among Danish men and women in late midlife

OBJECTIVE

The objective of the present study is to describe the prevalence of allostatic load (AL) among Danish men and women in late midlife, and if there is a social gradient in AL.

METHOD

A total of 5,420 participants from the Copenhagen Aging and Midlife Biobank (CAMB) aged 48 to 63 years (68.5% men, 31.5% women) underwent a health examination including standardized measures of height, weight, body fat, and blood pressure in 2009-2011. AL (range 0-14) was established by summing the scores of the poorest quartile for each of 14 biological variables related to the metabolic and immune systems.

RESULTS

We found a social gradient in AL in late midlife among men and women living in Denmark.

DISCUSSION

AL may be a potential biomarker for early aging in countries with a strong social welfare system. It is important for intervention studies to be aware of this type of biological vulnerability already present in late midlife.

An interlaboratory comparison between similar methods for determination of melatonin, cortisol and testosterone in saliva

An interlaboratory comparison study for melatonin, cortisol and testosterone in saliva in which five laboratories participated is reported in this study. Each laboratory blindly measured eight samples prepared from natural saliva spiked with melatonin, cortisol and testosterone in the range 0-579 pmol/L for melatonin, 0-90 nmol/L for cortisol, and 0-622 pmol/L for testosterone. The recovery of spiked material for melatonin ranged from 91-110%, from 83-100% for cortisol and from 80-94% for testosterone. The content of natural hormone in saliva was estimated to be between 0.278 and 6.90 pmol/L for melatonin, 0.56 and 6.72 nmol/L for cortisol and 11.9 and 73.8 pmol/L for testosterone. This indicates a large interlaboratory variation. The present study emphasizes the importance of external quality control for the analysis of melatonin, cortisol and testosterone in saliva.

Development and evaluation of a liquid chromatography tandem mass spectrometry method for simultaneous determination of salivary melatonin, cortisol and testosterone

Circadian disruption can have several possible health consequences, but is not well studied. In order to measure circadian disruption, in relation to shift or night work, we developed a simple and sensitive method for the simultaneous determination of melatonin, cortisol and testosterone in human saliva. We used liquid-liquid extraction (LLE) followed by liquid chromatography coupled to electrospray tandem mass spectrometry (LC-ESI-MS/MS) recorded in positive ion mode. Saliva samples were collected by spitting directly into tubes and 250 μL were used for analysis. The limits of detection were 4.1 pmol/L, 0.27 nmol/L and 10.8 pmol/L for melatonin, cortisol, and testosterone, respectively. The developed method was sensitive enough to measure circadian rhythms of all 3 hormones in a pilot study among four healthy volunteers. It can therefor be used to study the impact of night work and working in artificial light on the workers circadian rhythms. To our knowledge this is the first LC-ESI-MS/MS method for simultaneous determination of salivary melatonin, cortisol and testosterone.

Cortisol, estrogens and risk of ischaemic heart disease, cancer and all-cause mortality in postmenopausal women: a prospective cohort study

BACKGROUND

Chronic stress may affect morbidity and mortality through neuroendocrine changes, and the ratio of cortisol to sex steroid hormones has been suggested as a biomarker of stress. We aim to address a relation between the ratio of cortisol to estrogens (C/E) and risk of ischaemic heart disease (IHD), hormone-dependent cancers and all-cause mortality among postmenopausal women.

METHODS

Estradiol and cortisol were measured in a subset of 838 women randomly drawn from the second wave of the Copenhagen City Heart Study (n = 5297 examined in 1981-83) as well as among all women who developed hormone-dependent cancers after baseline. The participants were followed in nationwide registers until 2007, with < 0.1% loss to follow-up.

RESULTS

The C/E ratio was not associated with self-reported stress, and there were no clear associations with IHD (highest vs lowest quartile: HR = 1.23; 95% confidence interval 0.83-1.81), hormone-dependent cancers (0.69; 0.45-1.08) or all-cause mortality (1.10; 0.86-1.41).

CONCLUSIONS

The C/E ratio was not associated with morbidity and mortality in women, and we cannot replicate the robust findings of a relation between the cortisol to testosterone ratio and IHD previously reported in men. Whether the C/E ratio is a reasonable biomarker of stress is debatable.

Concentrations of cortisol, testosterone and glycosylated haemoglobin (HbA1c) among construction workers with 12-h workdays and extended workweeks

OBJECTIVES

Working on large scale construction sites have been shown to have severe health consequences in terms of increased risk of hospitalization and disability retirement compared to construction work in general. The aim of the present study was to investigate whether large scale construction work involving 12-h workdays and extended workweeks leads to insufficient recovery measured as increased catabolic and decreased anabolic metabolism.

METHODS

The study group comprised 40 male construction workers of which 21 had 12-h workdays and extended workweeks (56 h/workweek). The comparison group consisted of 19 male construction workers, who worked regular hours (37 h/week, weekends off). Measurements of concentrations of cortisol in saliva and free testosterone and glycosylated haemoglobin (HbA(1c)) in blood were made in a repeated measures design during 2 workweeks for both groups supplemented with 1 week off for construction workers with extended workweeks.

RESULTS

The diurnal profile of concentrations of salivary cortisol for construction workers with extended workweeks differed from the diurnal profile of salivary cortisol for those with regular work schedules (P < 0.001). The construction workers with extended workweeks tended to have 15% [95% CI -3%; 37%] higher concentrations of free testosterone in serum compared to construction workers with regular work schedules (P = 0.09). There were no differences between the two groups with respect to concentrations of HbA(1c). There was no increasing trend in concentrations of cortisol or decreasing trend in concentrations of testosterone during the extended workweek. The diurnal profile for concentrations of cortisol differed between workdays and days off for construction workers with extended workweeks (P = 0.003).

CONCLUSION

In conclusion, we observed no indications of insufficient recovery in terms of increased catabolic or decreased anabolic metabolism in construction workers with 12-h workdays and extended workweeks compared to construction workers with regular work schedules.

Evaluation of accuracy and uncertainty of ELISA assays for the determination of interleukin-4, interleukin-5, interferon-gamma and tumor necrosis factor-alpha

The comparison of analytical results calls for validation of the assays used, i.e. for the documentation of accuracy (trueness and precision), linearity and specificity. In addition, there is a growing demand for evaluation and documentation of traceability and uncertainty of analytical results. However, models for establishing the traceability and uncertainty of immunoassay results are lacking. Sandwich enzyme-linked immunosorbent assays (ELISAs) were developed for determination of the human cytokines interleukin-4 (IL-4), interleukin-5 (IL-5), interferon-y (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). The accuracy of each of the assays was evaluated in the ranges of 1-15 microg/l (IL-4), 0.001-1 microg/l (IL-5), 0.5-2.5 microg/l (IFN-T) and 0.14-2.2 microg/l (TNF-alpha). Other evaluated performance characteristics were the limit of detection (LOD), immunological specificity, and robustness. Traceability was ensured by the use of World Health Organization International Standards (WHO IS). An uncertainty budget, which combined the contribution from all known uncertainty components, was established for each cytokine ELISA. The between-run relative analytical standard deviation (RSDA) of the assessed ELISAs was found to be in the range of 11-18%, except for IL-5 where RSDA increased at decreasing concentrations. The LOD was 0.12 microg/l, 0.0077 microg/l, 0.0069 microg/l and 0.0063 microg/l for IL-4, IL-5, IFN-gamma and TNF-alpha, respectively. Traceability to the WHO IS was established for each of the cytokines. The combined relative standard uncertainty (U(result)/C(result)) was 28%, 22-62%, 28% and 24% for the IL-4, IL-5, IFN-gamma and TNF-alpha results, respectively. The major contributions to uncertainty came from the relative analytical standard deviation and from the uncertainty of the mass concentration of the WHO IS. The uncertainty of the WHO IS was not stated in the accompanying certificate and was evaluated by other means. The largest sources of uncertainty were located outside our laboratory. This means that the possibilities to improve the reliability of the results produced by the ELISAs are very limited. The task of evaluating measurement uncertainty would be much easier if producers of international reference standards reported the uncertainty of the value of standards. The model for evaluating uncertainty presented in this paper is applicable to other types of assays and to most analytical methods.

Interleukin-8 secretion from monocytic cell lines for evaluation of the inflammatory potential of organic dust

The potential of organic dust to induce inflammation in vitro can be viewed as a crude measure of the total biologically active compounds in a dust sample. The purpose of this study was to further develop an in vitro screening method for evaluation of potential hazard related to low doses of dust exposure using two monocytic cell lines (U937 and THP-1). Dust was obtained from schools in Copenhagen. U937 and THP-1 cells were stimulated with dust for 24 h and interleukin-8 secretion was measured. The initial slopes of the dose-response curves were used to calculate the inflammatory potential, or potency factor (PF), of the samples. In characterization of the method, lipopolysaccharide from Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Salmonella enteritidis were tested together with three glucans, nickel sulfate (NiSO(4)), methyl methacrylate (MMA), formaldehyde, and four surfactants. The PF values of LPSs in both monocytic assays ranked as follows: S. enteritidis> E. coli>K. pneumoniae/P. aeruginosa. The PF values of NiSO(4), MMA, formaldehyde, and the surfactants were zero or below. Using the THP-1 cell line, the PF values of dust samples were 30 times higher than when using the U937 cell line, and 7 times higher than when using the lung epithelial cell line (A549). The high sensitivity of the THP-1 bioassay makes it potentially useful as a screening tool for hazard evaluation of dust from, e.g., the indoor environment.

Seasonal and biological variation of urinary epinephrine, norepinephrine, and cortisol in healthy women

BACKGROUND

There is a significant circadian and seasonal periodicity in various endocrine functions. The present study describes the within-day and seasonal fluctuation for urinary catecholamines and cortisol and estimates the within- (CV(i)) and between-subject (CV(g)) coefficients of variation for healthy women undertaking their routine work. In addition, index of individuality (I(i)) and power calculations were derived.

METHODS

Eleven healthy females undertaking their routine life-style at work participated in the study. Each subject collected six samples during 24 h 15 days over a year, giving a total number of 990 samples. Using a random effect analysis of variance, we estimated CV(g) and total within-subject variation (CV(ti)), i.e. combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CV(ti) to give CV(i). CV(i) was estimated from samples collected monthly during 1 year (CV(iy)), weekly during 1 month (CV(im)), and six to eight times/day (CV(id)).

RESULTS

A seasonal variation was demonstrated for excretion of epinephrine, norepinephrine, and cortisol standardized with creatinine. Concentrations of urinary epinephrine were higher during June and July compared to the rest of the year, whereas concentrations of urinary cortisol were higher during December and January compared to the rest of the year. Excretion of norepinephrine was lower during working hours and higher during hours off work for June and July compared to the rest of the year. There was a high within- and between-subject variation, which could not be explained by menstrual cycle, behavioral, emotional, or cognitive stress reactions.

CONCLUSIONS

Despite high biological variation a reasonably low sample size, e.g. 10-50 individuals, is adequate for practical applicability, i.e. studying differences above 150%. The present study recommends to include the sampling time in the statistical evaluation of data and to be aware of the changes in diurnal variations over seasons. When single measurements are to be evaluated, reference intervals are recommended.

Seasonal and Biological Variation of Blood Concentrations of Total Cholesterol, Dehydroepiandrosterone Sulfate, Hemoglobin A1c, IgA, Prolactin, and Free Testosterone in Healthy Women

Background: Concentrations of physiological response variables fluctuate over time. The present study describes within-day and seasonal fluctuations for total cholesterol, dehydroepiandrosterone sulfate (DHEA-S), hemoglobin A1c (HbA1c), IgA, prolactin, and free testosterone in blood, and estimates within- (CVi) and between-subject (CVg) CVs for healthy women. In addition, the index of individuality, prediction intervals, and power calculations were derived.

Methods: A total of 21 healthy female subjects participated in the study. Using a random effects analysis of variance, we estimated CVg and total within-subject variation (CVti), i.e., the combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CVti to give CVi. CVi was estimated from samples taken monthly during 1 year (CViy), weekly during 1 month (CVim), and six times within 1 day (CVid).

Results: A cyclic seasonal variation was demonstrated for total cholesterol, DHEA-S, HbA1c, prolactin, and free testosterone. Within-day variation was shown for prolactin and free testosterone. The overall mean values for the group and the variability (CViy and CVg) were: 5.1 mmol/L, 5.5%, and 5.0% for total cholesterol; 6.6 μmol/L, 7.1%, and 21% for DHEA-S; 4.3%, 2.6%, and 3.3% for HbA1c/hemoglobintotal; 2.1 g/L, 5.9%, and 13% for IgA; 136 mIU/L, 23%, and 27% for prolactin; and 5.4 pmol/L, 21%, and 29% for free testosterone.

Conclusions: Collecting samples at specific hours of the day or times of the year may reduce high biological variation. Alternatively, the number of individuals may be increased and a paired study design chosen to obtain adequate statistical power.

Determination of the urinary metabolites of styrene: estimation of the method evaluation function and evaluation of reference values in Danish subjects

A European study on styrene exposure was initiated in 1989 to evaluate the health effects of environmental and occupational exposure. A part of this study included the development of an analytical method for use in a biological monitoring program. The urinary metabolites of styrene, mandelic acid (MA) and phenylglyoxylic acid (PGA) were quantitated by a direct and convenient high-performance liquid chromatography method. Urine samples were diluted with eluent and analysed by HPLC with a C8 reversed-phase column and a buffer to acetonitrile (9:1) eluent with a counterion added. The detector used was a variable UV detector and the wavelength was lambda = 210 nm. The method was statistically evaluated by a method evaluation demonstrating no systematic error. The uncertainty was 23.8 mumol/l and 11.5 mumol/l for MA and PGA, respectively. The limit of detection (LOD) of MA is 71.4 mumol/l and the LOD of PGA is 34.5 mumol/l, sufficiently low for the measurement of styrene exposure at a low exposure level. The present study indicates that reference values for MA and PGA are low. The fraction of reference values below LOD was 0.80 for MA and 0.66 for PGA; consequently, the reference values were described by a non-parametric one-sided tolerance interval. The 95% one-sided upper tolerance limits calculated for MA and PGA were 31.0 mumol/mmol creatinine and 20.1 mumol/mmol creatinine, respectively, with the coverage 0.95 +/- 0.045 for both metabolites. The method has been used for biological monitoring in several studies of environmentally and occupationally exposed subjects in concentrations up to 200 mumol/mmol creatinine for MA and 150 mumol/mmol creatinine for PGA.

Danish external quality assessment scheme: an interlaboratory comparison study on lead, cadmium and chromium in lyophilized human blood concentrate

A Danish External Quality Assessment Scheme (EQAS) was carried out by the Danish National Institute of Occupational Health during the period 1988-1992. The scheme was implemented for 29 international laboratories from 15 countries assaying lead, cadmium, and chromium in human blood to ascertain the systematic error and uncertainty of the analytical methods. In the survey the quality control material AMI B701-B705, based on lyophilized human whole-blood concentrate, were used. As an estimate of the true values the reference values used in this evaluation were (a) the computed values, i.e., sum of the basal and spiked trace element concentration, and (b) the consensus values normally used in the Danish EQAS. This international evaluation of lead, cadmium, and chromium in human blood demonstrated that the use of lyophilized human blood concentrate quality control materials combined with this scheme is valuable in estimating the systematic error and the uncertainty of the analytical methods. For evaluating analytical performance, the computed values were preferable to the consensus values for lead and cadmium in human blood. Due to analytical difficulties suitable reference values were not established for chromium in blood. The study revealed analytical difficulties for cadmium and chromium in human blood. The assessment of laboratories according to established performance indexes indicates that few laboratories can maintain these performance indexes.