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PubMed2005

Risk assessment for severe postoperative hypocalcaemia after neck exploration for primary hyperparathyroidism.

BACKGROUND AND AIMS: A further development of the risk profile for severe postoperative hypocalcaemia after surgery for primary hyperparathyroidism (pHPT) was made with the aim of expanding the group of patients who can be discharged safely after 23 hours. METHODS: Prospective study with 156 consecutive pHPT patients (158 operations) during 2001 and 2002. Risk factors for postoperative severe hypocalcaemia (ionised calcium < 1 mmol/L), were (1) preoperative concentration of parathyroid hormone (PTH) > 35 pmol/L (five times the upper reference value, reference range 1.1 to 6.9), (2) history of previous neck surgery, (3) biopsy/excision of > 2 parathyroid glands or (4) concomitant thyroid surgery. RESULTS: The risk factors showed a sensitivity of 100 % (9/9). In 110 of the operations (70%) no risk factors were identified. Postoperative calcium levels were significantly lower after 48 operations with risk factor(s) identified, as compared to the group without risk factors (p < 0.01). Seven of 17 patients (41%) with PTH > 35 pmol/L developed severe postoperative hypocalcaemia. Two of 31 patients (6%) with PTH < 35 pmol/L in the presence of other risk factor(s) developed severe postoperative hypocalcaemia. CONCLUSION: Patients with no risk factor can safely been discharged from hospital on the first postoperative day. Patients with preoperative concentration of PTH > 35 pmol/ L (five times the upper reference value) should stay in hospital until nadir level of calcium is reached. Patients with concentration of parathyroid hormone less than 35 pmol/ L in the presence of other risk factor(s) may have an early discharge from hospital (second postoperative day) combined with outpatient measurements of calcium levels.

Adult↗

PubMed1992

Food and Drug Administration's proposed labeling rules for protein.

The labeling proposals of the National Labeling and Education Act (NLEA) and the Food and Drug Administration (FDA) are having enormous impact on the food industry. The comment period for the November 1991 rules ended February 25, 1992. The 1991 proposals, with possible modifications, may become law as soon as November 8, 1992; industry then has 6 months to comply. It is imperative that dietitians be familiar with the content and meaning of the new labels. The NLEA information needs to be introduced into academic curricula immediately. Not only will dietitians need to define for consumers the difference in the proposed new reference values--Reference Daily Intake (RDI) and Daily Reference Values (DRVs)--if implemented, but they will also need to understand the quantifiable statements underlying the various descriptors, eg, light, low, high, more, free, and source, for all nutrients and food attributes displayed on labels. This article describes the proposed changes for determining protein quality.

Dietary Proteins↗

PubMed1998

[Characterization and problems regarding clinical reference ranges of aged subjects on clinical chemistry].

Various characteristic clinical laboratory testing data related to clinical chemistry were collected from 11 institutes across the nation, and age-related clinical reference values, reference intervals and within-subject biological variations were calculated. Using these calculated results, characterization of aged-related reference ranges and the method of determining an aged subject's testing values were investigated. From these results, the following facts became clear. Estimation of health-associated reference intervals for aged subjects was very difficult. As the aged subject's reference values differ remarkably by sex and age on several test items, sex- and age-related clinical reference values are necessary. In case of the mass screening survey which utilizes preceding healthy values, we should decide by within-subject biological variation. We usually use reference ranges to decide whether the measured values are located within these ranges, and must use a differential value to speculate regarding a particular disease. These results indicate that multiple standard must be prepared for each clinical laboratory testing value, and that it is ideal to be able to select a suitable standard for the subjects state. To select a suitable standard clinically, we need an expert system. For this purpose, much more basic data concerning reference ranges, differential values and so on must be accumulated.

Aged↗

PubMed1985

Methods of assigning accurate values to reference serum. Part 1. The use of reference laboratories and consensus values, with an evaluation of a procedure for transferring values from one reference serum to another.

A method is described for transferring the accuracy of values obtained by reference laboratories from one serum, which is used as a calibration standard, to another, which is treated as the unknown test sample. Six batches of lyophilised horse serum, of closely similar composition, were analysed by 10 European reference laboratories during 1978-1982, and used to obtain transfer values for one masterlot of a similar serum. No evidence was found that the transfer process introduced any inaccuracy. A comparison has been made, for bilirubin, creatinine, iron, phosphate, total protein and urea, between transferred values, the results obtained by direct analysis of the masterlot by reference laboratories, and consensus values found in two independent external quality assessment schemes. The transfer technique enables an evaluation to be made of these different procedures for assigning values to reference serum, and may reveal methodological differences, such as those described for iron and creatinine.

Animals↗

PubMed1985

Methods of assigning accurate values to reference serum. Part 2. The use of definitive methods, reference laboratories, transferred values and consensus values.

Eight analytes (Ca, Cl, cholesterol, glucose, Mg, K, Na and urate) have been determined in one horse serum masterlot by up to six different procedures: (i) by so-called definitive methods; (ii) by a group of reference laboratories using a variety of analytical methods; (iii) using the results of two independent external quality assessment schemes; (iv) by transferring values from a human serum standard reference material analysed by definitive methods; (v) by similar transfer of values from several batches of horse reference serum previously analysed by definitive methods; and (vi) as in (v) but using a group of reference laboratories. The results have confirmed the validity and usefulness of the transfer process in value assignment and in identifying outliers due to inaccurate methods. Definitive methods are shown to be subject to error, and although they appear to be the most accurate single techniques currently available, they are not definitive in the sense of being without bias and having no known source of inaccuracy.

Animals↗

PubMed2002

[Dorsal and lumbar paraspinal electromyographic study. Multi-MUP analysis and drawing up normal values in a reference population].

OBJECTIVE: The aim of this study was to contribute to draw up reference values relating to electromyographic (EMG) parameters in dorsal and lumbar paraspinal muscles. MATERIALS AND METHODS: 75 healthy subjects without back pain underwent electromyography of multifidus bundles, which are innervated uni-segmentally by the dorsal ram of the spinal nerve. T8, L3, L4, L5 and S1 myotomes were systematically explored. Output variables were spontaneous denervation activity and quantitative EMG data obtained by multi-MUP (Motor Unit action Potential) analysis. RESULTS: No abnormal insertional or spontaneous activity (such as fibrillation, positive sharp waves or fasciculation) was recorded at rest. Neither sex nor age influenced motor unit action potential features in our series. Reference values were drawn up for T8 and L5 segmental levels using the mean values of 20 motor unit potentials in each patient studied, the reference interval being defined by the lower and the upper outlier limits on individual values. CONCLUSION: This study offers reference data to electromyographers to help better identifying possible myogenic or neurogenic pathological changes, especially in lumbosacral radiculopathies.

Adult↗

PubMed2006

Factors influencing lung function: are the predicted values for spirometry reliable enough?

Spirometric lung function parameters are used as a diagnostic tool and to monitor therapy effectiveness or the course of disease. On the other hand, forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC) are important predictors of morbidity and mortality in elderly persons. In clinical use, FEV(1) and FVC are measured in liters and usually each is expressed as a percentage of the predicted value. Reference values used for the prediction of lung function should be reliable. It seems crucial that the reference cohort be representative. There is no doubt that gender and height are the most important predictors of lung function. The third predictor, age, may be a confounding factor. The study of age-dependent changes in lung function through the lifespan reveals distinctive differences. The FEV(1) and FVC in adults are related to the maximum level attained, the plateau period, and the rate of lung function decline. A non-linear dependence between age and lung function parameters is more complex. The maximum level of lung function, possible to attain, is influenced by a genetic factor. The plateau and decline phases are closely connected with several independent predictors. In the last decade, some new factors influencing lung function have been established. A relation between lung function and hyperglycemia of diabetes mellitus is a novel field of interest. Also, the influence on lung function of waist size, weight, and body composition or muscle strength are underscored. These, previously not full well unrecognized, factors make it difficult to get accurate norms with regression equations, traditionally using sex, height, and age as predictors.

Aging↗

PubMedDate not supplied

[Problems in practical implementation of the external quality control program in clinical laboratory investigations].

Center for External Quality Assessment in Laboratory Medicine has been organized in Russia. The National External Quality Assessment Scheme for 16 common analyses in clinical chemistry was implemented in 1992 under governmental support. A total of 1180 laboratories wished to participate in the program. 636 laboratories presented the results of analyses of 4 control serum pools, 2 with normal and 2 with increased concentrations of the constituents. Each control pool was analyzed twice allowing separate estimation of the accuracy and precision. Accuracy was assessed as the bias from method-dependent means and reference values. Reference methods were implemented for sodium, potassium, total protein, cholesterol, and triglycerides. Analysis of variance demonstrated that the errors are mainly due to the variability of methodologies in different laboratories, this variability being negligible.

Analysis of Variance↗

PubMed1996

[Reference intervals, discussed again].

The concept of 'reference intervals' proposed by NCCLS DOCUMENT C28-P has been introduced in Japan, and it has been widely accepted among laboratory scientists and clinicians. However, the terms 'reference values' and 'reference intervals' appear to be misunderstood by some. Normal ranges which have been used conventionally should not be simply renamed 'reference intervals'. The term 'reference intervals' should be strictly reserved for the ones which are determined based on the NCCLS recommendation. However, it is not an easy work, almost impractical for most clinical laboratories to follow strictly the NCCLS document C28-P. Therefore, the author suggests [correction of suggest] a multi-institutional cooperative activity to establish the reference intervals; the reference intervals for 13 serum proteins among Japanese adults have been successfully determined with the cooperative work of 7 clinical laboratories. 'Reference values' in a strict sense has been defined by NCCLS to be the observed values among reference individuals. However, 'reference values' in a broad sense should be understood to be any consensus value set by a professional group(s) for the purpose of clinical decision making.

Decision Making↗

PubMed1995

Clinical efficiency of in vitro and in vivo tests for allergic diseases.

BACKGROUND: Specific serum IgE determination is widely used in the diagnosis of IgE-mediated allergic diseases but the relative merits of in vitro measurement of IgE antibody in comparison to in vivo skin tests are still debated. OBJECTIVE: The aim of this study was to investigate the clinical efficiency of a "second generation" technique for in vitro analysis of IgE antibody (Pharmacia CAP System). METHODS: Eighty-six patients with suspected inhalant and/or food allergies and 20 asymptomatic subjects for a total of 655 tests were evaluated. Sera with divergent results between in vitro and in vivo techniques were further analyzed by using ImmunoCAP inhibition and immunoblotting. For the calculation of sensitivity and specificity of both in vitro and in vivo tests we considered as true value (reference value) either the concordant results or, in case of discordance, the datum confirmed by ImmunoCAP inhibition or immunoblot (ie, vitro positive, vivo negative, ImmunoCAP inhibition positive; true result: positive). RESULTS: The obtained results demonstrate that the in vitro results correlate well in terms of specificity and sensitivity to this new reference standard. In particular a higher specificity for Pharmacia CAP System in comparison to in vivo skin prick test for grass pollens and a better sensitivity for mites and cat allergens were found. CONCLUSIONS: Our results suggest that the in vitro "second generation" testing provides reliable results in all clinical situations.

Adolescent↗

PubMed1986

Swelling of the foot, its vascular volume and systemic hemoconcentration during long-term constrained sitting.

Swelling of the left foot and changes in its vascular volume (VV) were studied in seven healthy subjects during 8 h of seated work without leg movements. Changes in total plasma volume (PV) were calculated from hematocrit values. Reference values (r.v.) were obtained during a working day requiring intermittent physical activity (walking). Significant changes during the first 4 h: the foot swelled by 3.5% (r.v.: 2.2%) and VV was reduced by 0.5% of the foot volume (r.v.: increased by 0.3%). Accordingly, the interstitial fluid volume (IFV) of the foot increased by 4.0% (r.v.: 1.9%). The loss of PV was 6.3%. During the last 4 h the only significant change was an increase in foot volume by 1.9%. It is concluded that (1) foot swelling should be corrected for changes in VV to obtain an exact measure of the change in IFV, (2) prolonged elevated pressure, assumed to occur in the feet during relaxed sitting, does not imply distension ("delayed compliance") of the vascular system as previously suggested, (3) hemoconcentration seems to reach complete stability during the initial period of quiet sitting, (4) loss of PV during sedentary work may be avoided by a modest increase in leg activity.

Blood Volume↗

PubMed2004

Plasma B-type natriuretic peptide reflects left ventricular hypertrophy and diastolic function in hypertension.

BACKGROUND: Hypertension is associated with changes in concentrations of vasoactive peptides and procollagen propeptides, but their relationships with left ventricular hypertrophy and cardiac function are unclear. METHODS: We measured plasma levels of atrial natriuretic peptide (ANP), its amino terminal propeptide (NT-proANP), B-type natriuretic peptide (BNP), endothelin-1 (ET-1), and serum levels of the aminoterminal propeptide of type I procollagen (PINP) and the aminoterminal propeptide of type III procollagen (PIIINP) and echocardiographic parameters in 97 patients with hypertension in the Anglo-Scandinavian Cardiac Outcomes Trial. RESULTS: Median values (reference values) of the peptides were: ANP 11.2 (6.9-14.9) pmol/l, NT-proANP 351 (143-311) pmol/l, BNP 1.1 (0.4-7.2) pmol/l, ET-1 8.7 (1.2-5.0) pmol/l, PIIINP 2.8 (1.7-4.2) microg/l and PINP 29 (19-84) microg/l. Plasma BNP levels in patients with left ventricular hypertrophy (1.2 pmol/l) and patients with echocardiographic signs of diastolic dysfunction (1.5 pmol/l) were greater than those in patients without hypertrophy (0.7 pmol/l) and normal diastolic parameters (0.9 pmol/l) (p<0.05). BNP was the only biochemical parameter that independently predicted interventricular septal diastolic diameter (p<0.05), left ventricular mass index (p<0.01) and ratio of the velocity-time integrals of the E and A waves of the mitral inflow in a stepwise logistic regression analysis (p<0.05). CONCLUSIONS: The results show that BNP reflects the remodelling process in hypertension.

Adult↗

PubMed2000

The relation between mitral annulus motion and ejection fraction changes with age and heart size.

Mitral annulus motion (MAM) has recently been introduced as an index of left ventricular function. Several echocardiographic studies have shown good agreement between ejection fraction (EF) and MAM x 5, where MAM is the total mitral annulus motion, measured in mm, and EF is expressed as a percentage. This means that if MAM is used for estimation of left ventricular function, the conversion factor 5 is used, if the function is expressed as EF. In these studies, the mean age of the patients was over 60 years. The present study, including 102 patients, shows that in patients aged 20-40 years, the conversion factor is about 4.3, in patients aged 41-60 years it is about 4.6 and in patients aged 61-80 years it is about 5.0. It was also found that the ratio EF/MAM decreases with increasing height and left ventricular diameter, both variables closely connected to heart size. The results suggest that when MAM is used in assessment of left ventricular function, it is unwise to express the function in terms of EF. It is preferable to use MAM as a direct index of ventricular function, using reference values referred to aged and height. If the estimated function is expressed in terms of EF, different converting factors must be used depending on the age of the patients.

Adult↗

PubMed1993

[Effect of adaptation and compensation mechanisms on postoperative function of patients with tumors of the oral cavity].

To examine adaptation and compensation mechanisms on oral function, the tongue and the floor of the mouth of five healthy volunteers were immobilised with a plastic plate. The functional results of this group were compared with the postoperative results of patients with tumours in the area of the anterior floor of the mouth and the edge of the tongue. Swallowing, sucking, and speech functions were used to assess oral function. Unhandicaped swallow and sucking functions were determined as average value (reference value 100%) in a control group with 20 healthy adults. The results of the study demonstrate the adaptive ability of the tongue and underline the importance of keeping the remaining structures free to move. In cases of resection in the area of the anterior floor of the mouth, however, careful soft tissue reconstruction plays a far greater role, since the remaining structures do not adapt as easily.

Adaptation, Psychological↗

PubMed2005

Monitoring temporary immunodepression by flow cytometric measurement of monocytic HLA-DR expression: a multicenter standardized study.

BACKGROUND: Single-center trials have shown that monocytic HLA-DR is a good marker for monitoring the severity of temporary immunodepression after trauma, major surgery, or sepsis. A new test for measuring monocytic HLA-DR is now available. METHODS: We evaluated a new test reagent set for monocytic HLA-DR expression (BD Quantibritetrade mark HLA-DR/Monocyte reagent; Becton Dickinson) in single-laboratory and interlaboratory experiments, assessing preanalytical handling, lyse-no-wash (LNW) vs lyse-wash (LW) values, reference values, and the effect of use of different flow cytometers and different instrument settings on test variance. RESULTS: For preanalytical handling, EDTA anticoagulation, storage on ice as soon as possible, and staining within 4 h after blood collection gave results comparable to values obtained for samples analyzed immediately after collection (mean increase of approximately 4% in monocytic HLA-DR). Comparison of LNW and LW revealed slightly higher results for LNW ( approximately 18% higher for LNW compared with LW; r = 0.982). Comparison of different flow cytometers and instrument settings gave CVs <4%, demonstrating the independence of the test from these variables and suggesting that this method qualifies as a standardized test. CV values from the interlaboratory comparison ranged from 15% (blood sample unprocessed before transport) to 25% (stained and fixed before transport). CONCLUSIONS: For the BD Quantibrite HLA-DR/Monocyte test, preanalytical handling is standardized. Single-laboratory results demonstrated the independence of this test from flow cytometer and instrument settings. Interlaboratory results showed greater variance than single-laboratory values. This interlaboratory variance was partly attributable to the influence of transport and can be reduced by optimization of transport conditions.

Flow Cytometry↗

PubMed1986

[Phantom substances in the quantitative evaluation of magnetic resonance T-images. II. Effect of relaxation times on magnetic resonance T-intensity values].

Reference material for quantitative MR Imaging (paramagnetic agar gel) is examined with regard to effects of small T1 and T2 variations on MRI signals. For some pulse sequences that are important in clinical practice, it can be shown that SE images are very sensitive to T2 variations, whereas IR images are influenced by both T1 and T2.

Electron Spin Resonance Spectroscopy↗

PubMed2006

Inter-laboratory comparison of NO2 and SO2 generated by dynamic dilution system under laboratory conditions: a technical discussion.

A workshop on analytical quality control (AQC) of ambient air quality measurement methods for nitrogen dioxide (NO(2)) and sulphur dioxide (SO(2)) was conducted by Central Pollution Control Board (CPCB) for officials involved in National Ambient Air Quality Monitoring (NAAQM) in India. Concentrations of NO(2) and SO(2) were generated by dynamic dilution system under laboratory conditions at low and high levels and measured using static dilution system and wet chemical methods laid down by CPCB under section 16(2)(h) of the air act 1981. CPCB provided the measured values as reference values for comparing the means obtained by the officials participated from thirteen organizations. A tolerance limit of +/-15% of the reference values was specified to accept the results. Generated concentrations, which were unknown to the participants, were measured using gaseous sampling assembly (Envirotech APM 411, New Delhi, India), and wet chemical methods laid down by CPCB i.e. the same methodology which is used by the organizations to generate the data of NO(2) and SO(2) in ambient air. Simultaneously, concentrations were checked by CPCB using automatic analyzers as a check on reference concentration. It is observed that results of automatic analyzers for NO(2) and SO(2) were within a tolerance of +/-5% with %RSD below 3. On the other hand, results of most of the participants showed variability in the measurements with %RSD ranging between +/-0.8 and +/-88.6 and exceedences of means from the tolerance limit with bias ranging between 1.4 and -59%. To check the cause of high variability in the measurements obtained under identical conditions, duplicate sampling was performed by one of the participants for SO(2) at low concentration level. In this study, results of wet chemical methods, automatic analyzers and results of duplicate sampling are analysed statistically to assess the cause of high variability in the measurements. Analysis of t-test and analysis of variance (ANOVA) showed highly significant results for NO(2) and SO(2) at high concentration levels (alpha 0.05) and for SO(2) at both the levels (alpha 0.01) respectively indicating some bias is existing either in the sampling or in analytical technique. Duplicate sampling performed to check precision in parallel measurements showed high %RSD indicating the presence of systematic error in sampling technique as the same calibration factor (CF) was used to measure the concentration of duplicate samples. Statistical analysis of flow rates of duplicate sampling showed that the sampling assembly could not maintain the constant flow rate within the +/-10% with that measured at the start of the sampling. This resulted in high %RSD and deviation from the reference values for the results of most of the participants, even after accepting +/-15% tolerance limit. There is a need to improve and evaluate this gaseous sample collection device under laboratory conditions to generate reliable database of NO(2) and SO(2) in ambient air.

Analysis of Variance↗

PubMed2003

Impact of serum creatinine measurement error on dose adjustment in renal failure.

BACKGROUND: Doses of renally eliminated drugs should be adjusted according to kidney function to prevent adverse drug events and cost. Dose adjustment can be based on serum creatinine level, subsequent creatinine clearance estimation, and dosage calculation with consideration of the renal elimination properties of the respective compound. OBJECTIVE: Our objective was to quantify the impact and relevance of serum creatinine measurement error on dose adjustment in renal failure. METHODS: We analyzed 27914 measurements from external quality assessment surveys of 1878 German laboratories that used a kinetic alkaline picrate (69% of results) or an enzymatic method (25%) for creatinine determination. Linear models were fit for both methods combined and separately. On the basis of 95% confidence intervals (CIs) for creatinine values, 95% CIs for drug dosing were calculated. RESULTS: The 95% CI for a measured serum creatinine value was 0.80. Measured value < Reference method value < 1.28. Measured value for the kinetic alkaline picrate method and 0.87. Measured value < Reference method value < 1.21. Measured value for the enzymatic method. Applied to a data set of 6.5 million simulated patients with all possible combinations of characteristics relevant for drug dosing, the dosing error caused by serum creatinine measurement error did not exceed 25% in patients with creatinine clearance estimates lower than 50 mL/min according to the Cockcroft-Gault equation. For drugs completely eliminated by the kidneys in active form, the dosing error was up to 6-fold smaller than that which would occur if doses were not adjusted. CONCLUSION: The serum creatinine measurement error of current laboratory methods is small and is comparable to other errors influencing dose adjustment.

Aging↗