Kerttu Irjala

Time‐resolved fluorometry (TRF)‐based immunoassay concept for rapid and quantitative determination of biochemical myocardial infarction markers from whole blood, serum and plasma

We report the development of a time-resolved fluorometry-based immunoassay concept for the rapid measurement of three cardiac markers from whole blood, serum or plasma. Using a universal all-in-one (AIO) dry reagent concept, all the analyte specific reagents are built into a single microtire well, to which an identical assay protocol is applied. Addition of 5-20 microL sample (whole blood, serum or plasma) together with a universal buffer initiates the reaction, which is brought close to equilibrium in 15 min. After the wash step the Eu chelate-derived signal is measured directly from the dried surface. Application of this concept to the three cardiac markers illustrates its ability to provide rapid, highly sensitive and fully quantitative results over a large dynamic range with good reproducibility. Such a performance, especially when using whole blood specimens, is largely a consequence of the inherently fluorescent and stable Eu-chelate employed in the system. Correlation to commercial assays was excellent for all three analytes, as was between-sample matrix correlation using the AIO assays. The presented assay concept enabling a simple automation is particularly suited for point-of-care applications, where the performance characteristics are fully comparable to state-of-the-art central laboratory immunoassays.

Long‐term follow‐up of renal function after high‐dose methotrexate treatment in children

High‐dose methotrexate (HD‐MTX) is commonly used in treatment of pediatric leukemias and lymphomas. Transient deterioration in renal function is frequently noted during HD‐MTX treatment, but possible long‐term changes are less well known. In this study we aimed to study long‐term renal prognosis after HD‐MTX treatment, and to find possible underlying risk factors for reduced renal function.

Comparison of glomerular function tests in children with cancer.

Evaluation of renal function should be performed as part of the follow-up during and after chemotherapy in pediatric cancer patients. The aim of this study was to compare an isotope clearance method [isotope glomerular filtration rate (iGFR)] with alternative methods to determine GFR in such patients. Isotope GFR [99mTc-labeled diethylene triaminopentoacetic acid (DTPA) or 51Cr-labeled ethylenediaminetetra-acetate (EDTA)] was measured in 36 children (112 studies) and compared with simultaneously measured creatinine clearance (CrCl), serum creatinine (SCr), and cystatin C (CysC) concentrations, as well as the results of Schwartz, Counahan–Barratt, and Cockroft–Gault formulae, using general linear mixed models. Our results showed a significant association between iGFR and CysC concentrations (p < 0.001). No linear relationship was observed between CrCl and iGFR (p = 0.7). As expected, the results of height-based formulae (Counahan–Barratt and Schwartz) had significantly (p = 0.004) better correlation to iGFR than the results of a formula based on weight (Cockroft–Gault) (p = 0.19). Despite significant linear correlation, intraclass correlation coefficients showed poor agreement. Tests of similarity between iGFR estimates showed differences between average values of GFR. Therefore, determination of iGFR remains the method of choice in estimation of GFR in cancer patients. In our study population, assay of serum CysC was the most reliable alternative method to measure glomerular function.

Serum total renin, an independent marker of the activity and severity of retinopathy in patients with IDDM

BACKGROUND/AIMS Recent studies have demonstrated marked renin and prorenin concentration gradients between ocular tissues and blood, and local expression of the renin-angiotensin system (RAS) in the eye. The authors determined whether serum total renin, which mostly consists of prorenin, is a marker of the activity and severity of diabetic retinopathy independent of other microvascular complications. METHODS Total renin concentrations (TRC) were measured with a time resolved immunofluorometric assay in 38 patients with IDDM (age 34 (SD 7) years, duration of disease 22 (7) years, serum creatinine 95 (15) μmol/l, urinary albumin excretion rate (UAER) 207 (829) μg/min, HbA1c 8.5% (1.2%)), and in 13 matched normal subjects. All subjects were carefully characterised with respect to the presence and severity of retinopathy (RP score), nephropathy, and neuropathy using seven different tests of autonomic neuropathy. RESULTS Serum TRC was on average twofold higher in IDDM (396 (SE 211) ng/l) than in normal subjects (201 (88) ng/l, p<0.001). It was nearly twofold higher in patients with preproliferative or active proliferative retinopathy requiring careful follow up or therapy (TRC 596 (268) ng/l, n=11) compared with those with quiescent proliferative retinopathy after laser treatment (TRC 338 (183) ng/l, p<0.01, n=5); moderately severe non-proliferative retinopathy (337 (106) ng/l, p<0.01, n=13), no retinopathy, or only minimal non-proliferative retinopathy (270 (43) ng/l, p<0.001, n=9). In multiple linear regression analysis, RP score (p<0.01), but not the UAER or any index of autonomic neuropathy, was an independent determinant of serum TRC, and explained 32% of its variation (R=0.57, p<0.005). CONCLUSIONS Serum TRC in patients with diabetic retinopathy is increased independent of renal function and autonomic neuropathy, especially in those with severe active changes requiring careful follow up or treatment. These findings support the idea that diabetic retinopathy is the most important determinant of serum TRC in patients with IDDM, and that TRC is produced when retinopathy is active.

7.5 Common Reference Intervals for Plasma Proteins in the Nordic Countries

It is a philosophic question whether it is possible to establish common reference intervals valid for different ethnic groups and geographical areas. From a practical viewpoint, however, reference intervals are in current use and seem to be the best tool for a general validation of the first results from persons consulting the health care system

Circulating oxidised LDL lipids, when proportioned to HDL-c, emerged as a risk factor of all-cause mortality in a population-based survival study

BACKGROUND AND OBJECTIVE the data concerning the predictive role of oxidised LDL (ox-LDL) in all-cause mortality are scarce. We investigated whether circulating ox-LDL would stand out as a risk factor of total mortality in the elderly. Study subjects, design and methods: a total of 1,260 elderly inhabitants (533 men, 727 women) aged 64 years or more from Lieto, South-Western Finland participated the study in 1998-99. Medical records were re-examined approximately a decade later in January 2009. Circulating ox-LDL lipids were used as the main outcome measure. The comparisons were obtained by the Cox hazard ratio model. RESULTS during the 10-year follow-up, 467 participants had died (37%), of whom 36% had died of atherosclerotic cardiovascular diseases. Ox-LDL was a significant predictor of all-cause mortality, when proportioned to low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c) or apolipoprotein A1 (apoA1). These findings were independent of age, sex, body mass index, smoking, blood pressure and diabetes (P < 0.05 for all). CONCLUSION circulating ox-LDL lipids, when proportioned to LDL-c, HDL-c or apoaA1, stand out as a risk factor for all-cause mortality independent of major confounding attributes. In the prospective survival and increasing disease burden caused by accumulating age, oxidative stress may have a considerable role.

Effects of health advocacy, counseling, and activation among older coronary heart disease (CHD) patients

Background and aims: Coronary heart disease (CHD) is common and the maprity of CHD patients are 65 years or older. There exist only a few randomized, controlled intervention studies on secondary prevention of CHD among elderly CHD patients. Our study assessed the effects of health advocacy, counseling, and activation programs with outcome variables of changes in the use of fats, lipid-lowering medications, frequency of exercise, cigarette smoking, serum cholesterol and triglyceride concentrations, blood pressure, and symptoms of late-life CHD among CHD patients of the Lieto Study. Methods: Randomized, controlled intervention study. Late-life (>65 yrs) CHD patients were randomized into intervention group (IG) (n=118) and control group (CG) (n=109). Intervention consisted of 16 lectures by experts, eight group discussions, six group exercise sessions, and three social activity events. Results: The use of lipid-lowering medications became more common in IG than in CG among men (p=0.041), with a similar tendency among women. Among women, decreases in the means of total serum cholesterol (p=0.009) and LDL-cholesterol (p=0.049) were greater in IG than in CG. Conclusions: The program produced no positive effects on health behavior. Positive effects were gained by the increase in lipid-lowering medications, which reduced mean total serum cholesterol and LDL-cholesterol concentrations. More intensive counseling on health behavior should be planned, implemented, and evaluated.

Prolonged endocrine responses to medroxyprogesterone in postmenopausal women With respiratory insufficiency

Objective To evaluate the endocrinologic changes associated with, and possibly responsible for, prolonged ventilatory improvement after short-term medroxyprogesterone acetate (MPA) in chronic respiratory failure. Methods Fourteen postmenopausal women with permanent or previous episodic hypercapnic or hypoxemic respiratory failure were enrolled in a placebo-controlled, 12-week, single-mask trial including 14-day treatment periods with placebo and MPA (60 mg daily) and a 6-week follow-up. We evaluated the duration of MPA-induced alterations on serum concentrations of progesterone, estradiol, testosterone, FSH, LH, sex hormone–binding globulin (SHBG), and prolactin. Hormones were measured four times: at baseline, after 14 days with MPA, and during the washout on days 21 and 42. Results With MPA, FSH decreased 42.7% (P < .001, 95% confidence interval [CI] −54.2, −31.6), LH 62.1% (P < .01; 95% CI −81.0, −32.6), and SHBG 58.1% (P < .001; 95% CI −63.0, −43.9). Luteinizing hormone remained decreased (−28.7%; P < .01; 95% CI −42.0, −14.2) at the 3-week washout, whereas FSH and SHBG were back to pretreatment levels. Prolactin had a borderline initial increase of 23.5% (P = .097; 95% CI −3.5, 50.5) with MPA and a significant increase at the 3-week (31.9%; P < .05; 95% CI 1.0, 62.9) and 6-week (26.4%; P < .05; 95% CI 4.4, 48.3) washouts. Conclusion Medroxyprogesterone acetate 60 mg daily for 2 weeks has both immediate (FSH, LH, and SHBG), prolonged (LH), and rebound endocrinologic (prolactin) effects up to 6 weeks after treatment. The MPA-induced widespread endocrine aftereffects could explain the earlier reported prolonged ventilatory improvement.

Discrepancy between total white blood cell counts and serum C-reactive protein levels in febrile children

Total white blood cell (WBC) counts and serum C-reactive protein (CRP) are used as inflammatory markers in febrile children. We studied the occurrence and clinical significance of discrepancy in these markers. From a 2-y period, we retrospectively reviewed the medical records of febrile children (≥1 month of age) with WBC ≥15×109/l and/or CRP levels ≥80 mg/l, as well as of children with lower values in both these parameters. WBC and CRP were discordant in 556 children and concordantly high in 194 children. A severe bacterial disease was presumed in 57% of children with concordantly high WBC and CRP, in 20% of those with discordant values, and in 5% of those with low levels of these markers (p<0.001). Non-streptococcal tonsillitis was the most common viral infection associated with elevated WBC and CRP. In conclusion, WBC and CRP are commonly discrepant in febrile children. Measuring both markers increases substantially the detection rate of bacterial infections.

5.1 External Analytical Quality Assurance for Proteins

In the Nordic Protein Project an external control scheme (external quality assessment) was combined with the two other indispensable aspects of analytical quality, i.e. standardization (with a common high quality calibrator) and specification of needed analytical quality for sharing common reference intervals for nine serum proteins in the Nordic countries. The quality specifications are reliable for the purpose and given in clinical chemical terms - ready for application to the control systems. Further, a control design for disclosing external and internal errors, separately, is designed with respect to calibration and robustness towards analytical interference from turbid patient samples.