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Results for “Repeatability and Reproducibility”

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PubMed1992

The in vitro radiosensitivity of lymphocytes from chronic lymphocytic leukaemia using the differential staining cytotoxicity (DiSC) assay. I--Investigation of the method.

A tumour sensitivity assay, the differential staining cytotoxicity (DiSC) assay, which has been shown to have potential in predicting tumour response to cytotoxic drugs, has been developed to investigate the radiosensitivity of peripheral blood lymphocytes isolated from patients with chronic lymphocytic leukaemia (CLL). The method involved irradiating isolated lymphocytes (0.64-20.48 Gy at 8 x 10(5) cells/ml) and incubating for 4 days. Subsequent radiation-induced cell kill was assessed by differential staining of dead and live cells and calculation of tumour cell viability. Factors affecting assay success rate and in vitro radioresponse were investigated. Results were shown to be reproducible both when repeat assays were performed on the same specimen on the same day, and on different specimens from the same patient after intervening periods of time. Greater than 1 day transit time (whole blood) or storage (separated cells in medium) was found to be detrimental to assay success, but pH of the medium (either pH 7.3 or 8) had little effect. An increased incubation period (from 4 to 7 days) slightly reduced cell survival, but the underlying radioresponsiveness of the cells did not change.

Cytological Techniques↗

PubMed2001

Localization of the initial fibrillatory cycle in patients with paroxysmal atrial fibrillation.

BACKGROUND: Recent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysmal atrial fibrillation (AF). OBJECTIVE: To explore the location of intra-atrial conduction delay associated with initiation of AF. DESIGN: In 8 lone AF patients (51 +/- 10 years), 20 AF paroxysms were induced during electrophysiological examination. Bipolar electrograms were acquired from a 10-polar catheter in the coronary sinus (CS), a 4-polar His bundle catheter, and a 20-polar Halo catheter in the right atrium. RESULTS: Induced AF paroxysms showed earliest registered atrial activity in interatrial septum (IAS) or proximal CS in 17 cases (85%). Conduction delay at the posterior IAS or proximal CS accompanied induction of 18 AF paroxysms (6 patients). Atrial activation sequence at the beginning of the AF paroxysms was stable and reproducible in six repeatedly induced AF episodes (3 patients). CONCLUSION: In lone AF patients, induction of AF is associated with conduction disturbances in the IAS and proximal CS regions.

Adult↗

PubMed2006

Reliability and sensitivity of jerk-cost measurement for evaluating irregularity of chewing jaw movements.

Rate of change in movement acceleration (jerk) is a universally accepted quantity to evaluate irregularities of human limb and eye movements. This study was aimed to attest reliability of the jerk measurement of masticatory jaw movements and to identify its sensitivity to discriminate between movements performed with the presence of varied occlusal interference. Jaw movements during gum chewing were recorded with a 3D tracking device. Twelve adult subjects participated in the experiments. For five subjects, normalized jerk-costs (NJC) during jaw closing were compared between those measured on two separate occasions. For seven subjects, the NJCs during closing were compared with those measured with/without introduction of four different types of occlusal interference. The NJCs did not differ significantly between the two recording occasions. The interference at the canine tooth induced greater increase in the NJCs than that at the molar tooth. The comparison between repeated measures revealed reproducibility of the NJCs. In addition, the NJC was shown to be capable of discriminating between irregularities of the movements induced by occlusal interference at the canine and molar tooth sites. These findings suggest that the NJC is a valid indicator of masticatory jaw movement irregularity induced by disturbances of full intercuspation between upper and lower teeth.

Adult↗

PubMed1983

Bacteremia due to Pseudomonas aeruginosa: use of a combined typing system in an eight-year study.

P aeruginosa bacteremia is a nosocomial disease with a high mortality occurring in colonized, debilitated, and leukopenic patients and in those receiving immunosuppressive and antimicrobial agents [2]. Outbreaks of P aeruginosa bacteremia have often been associated with environmental reservoirs [3]. The 190 strains of P aeruginosa described in this study represent single isolates from bacteremic patients during an eight-year period. Representing about 50% of total isolates, the most common pyocin types were 1b, 3, and 10, immunotypes 1, 2, and 3 + 7, and serotypes 11, 6, and 1. Of the 37 known pyocin types, only 10 were represented in this study. All seven immunotypes and 14 of 17 serotypes were found. The overall typability for each of the three techniques was 88%-90%; however, the largest numbers of typable patterns were found when all three typing methods or pyocin and either immunotyping or serotyping were used. The smallest number of typing patterns occurred when immunotyping and serotyping were performed together. Correlation among the following types was greater than 50%; pyo 3:immuno 1:sero 6; pyo 10:immuno 2:sero 11, and pyo NI:immuno 4:sero 1. Upon repeated testing the reproducibility of types for each technique was 98%-100%. For the most precise epidemiologic studies of P aeruginosa infections all three typing methods should be employed.

Humans↗

PubMed1992

Prevalence and mechanism of streptokinase-induced platelet stimulation. Effect of acetylsalicylic acid.

It was recently shown that streptokinase may induce clot formation in vivo by immunoglobulin G mediated platelet stimulation. We evaluated the in vitro effect of streptokinase on platelet function in 103 subjects, of whom 52 were < or = 30 years and 51 were > or = 50 years old. Although streptokinase inhibited platelet aggregation in the majority of cases, in nine the threshold concentration of ADP required to induce irreversible aggregation decreased with streptokinase (1 million Units. l-1) by 30% or more. This observation was confirmed in five of the nine by repeated measurements indicating reproducible streptokinase-induced platelet stimulation. Among the five, two were < or = 30, and three were > or = 50 years old. In none of the five subjects did the radio allergo sorbent test detect type E immunoglobulins directed against streptokinase in the serum. In contrast, in four of the five subjects, streptokinase-induced platelet hyperaggregability was suppressed by addition of goat antibodies against human immunoglobulin G, or F(ab')2-fragments of such antibodies. Acetylsalicylic acid did not prevent streptokinase-induced platelet stimulation, but in three of five cases, led to an increase in the control threshold concentration for ADP, so that after the decrease induced by streptokinase the threshold concentration for ADP was in the same range as before acetylsalicylic acid and streptokinase administration. Thus, streptokinase led to an inhibition of platelet aggregation in the majority of subjects evaluated. In a minority of five out of 103, however, streptokinase reproducibly caused platelet stimulation, presumably mediated by immunoglobulin G.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Measurement of cutaneous blood flow by clearance of hydrogen gas generated by electrolysis.

In an attempt to assess the reliability of a method for measurement of local blood flow-namely, the clearance of electrochemically generated hydrogen gas-a series of experiments were conducted using the skin and skin flap in rats and rabbits. The results showed high accuracy in obtained values, good reproducibility in the repeated measurements, and consistency with the values obtained by the hydrogen gas inhalation method. Histological examination revealed only minimal damage to the tissue resulting from the measurement. Using this method, blood flow was measured at different sites on the flap in rats. The critical point of blood flow as measured by this method was thoroughly consistent with the dye distance as well as with the survival length. No injurious effects of the measurement procedure on flap survival were noticed. The present study suggests a wide potential application of this method in plastic surgery because of its high reliability and because no radioactivity is involved.

Animals↗

PubMed1981

Regional pulmonary ventilation measurements by xenon enhanced dynamic computed tomography: an update.

New developments in computed tomographic technology permit rapid, serial images that may yield information concerning tracer kinetics through a large tissue volume. One possible application of these developments is the derivation of local lung ventilation by observing the temporal changes of stable xenon concentrations. Preliminary results from six multilevel ventilation studies in dogs demonstrate that the lung may be repeatedly imaged during reproducible phases of respiration even when interscan table incrementation is employed to survey a number of tissue segments and breathing is permitted between scans. In addition, subanesthetic xenon concentrations provide adequate enhancement for possible quantification.

Animals↗

PubMed2005

Interlaboratory comparison of three methods for the determination of the radon exhalation rate of building materials.

In this study three methods for the determination of the radon (222Rn) exhalation rate of building materials are compared. All three are so-called purge-and-trap methods in which the sample is enclosed in a container from which the exhaled radon is continuously purged by a constant flow of nitrogen gas. The outflowing radon is directed through a trapping agent, and the radon exhalation rate is subsequently calculated from the trapped activity. The main differences between the three methods are the trapping agent (silica gel, charcoal), trapping temperature (liquid nitrogen, room temperature), trapping period (30 min to 10 d), analytical method to determine the trapped activity (liquid scintillation counting, gamma ray spectrometry, total gamma counting) and the sample counting times (1 to 16 h). The repeatability and intralaboratory reproducibility are determined for one of the methods and amount to 3.1% and 4.3%, respectively. The intralaboratory reproducibility, derived from five samples with a radon release rate up to 450 microBq s(-1), was found to be 5.6% on average (range 3 to 8%). These figures are close to the combined standard uncertainty of the individual results that vary between 3 to 6%, depending on the method and method variables such as trapping period and the uncertainty of the calibration source. Furthermore, another 10 commercially available building materials were analyzed to investigate the correlation between the applied methods. Using linear regression analysis, it was found that the slope deviated not more than 10% from the one to one correspondence line. The results show that measurements of the exhalation rate can be carried out with a large degree of accuracy provided sufficient care is taken for a well-documented standard method.

Calibration↗

PubMed1989

Beta-adrenergic receptor responsiveness to isoprenaline in humans: concentration-effect, as compared with dose-effect evaluation and influence of autonomic reflexes.

1. Different techniques of assessing beta-adrenoceptor sensitivity in vivo, by use of i.v. infusions or bolus injections of isoprenaline (ISO), were compared in healthy volunteers. The importance of autonomic reflexes for responses to ISO was evaluated by studying the influence of 'autonomic blockade' by atropine and clonidine, which antagonize muscarinic effects and reduce sympathetic activity, respectively. Estimates of in vivo responsiveness to ISO were compared with parameters reflecting beta 2-adrenoceptor function in vitro in lymphocytes. 2. Heart rate responses to infused ISO were not significantly altered by 'autonomic blockade' when evaluated from concentration-effect curves. When related to the infused dose of ISO, however, sensitivity was artefactually increased (P less than 0.05), as the plasma concentrations of ISO were 40% higher after atropine and clonidine. Heart rate responses to bolus injections of ISO were attenuated (P less than 0.05) by 'autonomic blockade', suggesting that facilitatory reflexes contribute to these non-steady state responses. Intersubject variations in heart rate responsiveness to ISO were greater than the intrasubject variability caused by counterregulatory reflexes. 3. 'Autonomic blockade' lowered venous plasma noradrenaline at rest. The noradrenaline response to ISO infusion was attenuated and the diastolic blood pressure response enhanced, indicating that a counterregulatory vasoconstrictor reflex normally is activated by ISO-induced vasodilatation. The plasma cyclic AMP response to ISO, on the other hand, was unaffected by atropine and clonidine and reflects beta 2-adrenoceptor responsiveness in vivo. 4. In vitro data for beta-adrenoceptor binding sites (Bmax;[125I]-IHYP binding) and cyclic AMP responses to ISO in lymphocytes correlated with DBP and noradrenaline responses to infused ISO. No correlations were found between in vitro data and heart rate, plasma cyclic AMP or plasma glycerol responses to infused ISO in vivo. 5. During prolonged ISO infusions (in six other healthy subjects) physiological responses reached greater than 90% of their steady state level after 8 min, but no definite steady state level could be defined for the plasma concentration of ISO during 40 min of infusion. 6. The ISO infusion test showed a good reproducibility, especially when repeated on the same day. Evaluation of plasma concentration-effect relationships increase the precision of the ISO infusion test as confounding inter- and intra-individual variations in ISO concentrations (as caused by e.g. autonomic blockade) will be taken into account.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1983

Kinetics of UV-erythema in normal subjects.

In the expanding field of clinical dermatopharmacology we standardized an erythema model for testing drugs with effects on UV-induced inflammation in normal male Caucasian subjects. Using a light source with fibre-optic transmission and precise radiation characteristics, some of the shortcomings of conventional UV-application could be overcome. The radiation geometry during the various experiments was kept constant by a tube, permitting a defined area of exposure. Up to eight skin areas of the backs of normal volunteers were radiated with 86.2% UV-A and 13.8% UV-B. After exclusion of hyporeactive and hyperreactive subjects a good intrasubject reproducibility was obtained repeatedly over at least 3 months. According to the definition of bioavailability, our method allows the measurement of the rate and extent of UV-induced erythema. This model has been used for testing topical steroids, non-steroidal antiphlogistics in a variety of pharmaceutical formulations.

Dose-Response Relationship, Radiation↗

PubMed1997

Study of the correlation between MEIA and ELISA methods for FK 506 determination in liver transplant recipients.

BACKGROUND AND OBJECTIVES: FK 506 is an immunosuppressive macrolide advocated for prevention of graft rejection. Plasma or blood FK 506 levels must be determined to strike a balance between FK 506 toxicity and graft rejection. The first aim of this study was to compare an automated microparticle enzyme immunosorbent assay (MEIA) method (on whole blood) with the reference enzyme-linked immunosorbent assay (ELISA) method (on plasma). A second aim was to compare the two methods for prediction of FK 506 nephrotoxicity. PATIENTS AND METHODS: Forty-seven patients were studied comprising 128 samples. All were treated with FK 506 on a compassionate basis. For each patient, the concentrations of FK 506 were determined in plasma by means of ELISA and in whole blood by MEIA. RESULTS: The repeatability and the reproducibility of these two methods were similar. The inter-patient correlation coefficient between MEIA and ELISA, determined on 128 samples from 47 liver recipients, was satisfactory (r = 0.82). From these 47 patients, the intra-patient correlation coefficients were calculated for 17 of them. The intra-patient correlation coefficients were between 0.63 and 0.98 for 15 patients, and between 0.26 and 0.55 in the remaining two cases. Mean creatinine plasma levels in the 55 samples below the median FK 506 value in the MEIA method and in the 55 with values above the median (120 and 134 mumol/litre, respectively) were significantly different (P < 0.05), as were those using the reference ELISA methods (115 and 139 mumol/litre, P < 0.01). In contrast, there was no significant difference between the mean creatinine plasma levels in the 55 samples with FK 506 levels below the median using both methods or between those above the median. CONCLUSION: The automated MEIA method, being simpler and more rapid than the ELISA method, should now be preferred for therapeutic monitoring of FK 506.

Adolescent↗

PubMed1992

Stress relaxation phenomenon in the healthy female urethra.

Following dilatation, urethral pressure declines over the next few seconds to a state of equilibrium. The stress relaxation parameter, Pt0.5, was defined as the relative pressure decrease 0.5 s after dilatation, where the pressures at 0.1 s and at the new equilibrium were set to 100% and 0% respectively. Pt0.5 was calculated from 171 urethral dilatations performed at each of 3 urethral sites of measurement in 10 healthy volunteers. It was found to be independent of the rate and size of urethral dilatation. It showed a fairly high reproducibility rate when repeated after 1 h and 1 week. Pt0.5 was calculated to approximately 60% with no variation along the urethra. The parameter is assumed to be useful in evaluating urethral sphincter function. Although the method can be performed without special urodynamic equipment, the frequency response of the pressure measurement system must be adequate.

Adult↗

PubMed1998

Validation of the [1,2-13C]acetate recovery factor for correction of [U-13C]palmitate oxidation rates in humans.

1. The validity of estimations of plasma fatty acid oxidation using tracers has often been questioned. The appearance of isotopic markers in breath CO2 is delayed and incomplete. Recently suggestions have been made that substantial amounts of tracer are incorporated into products of the tricarboxylic acid cycle (e.g. glucose, glutamine and glutamate) and that an acetate correction factor can be used to correct for tracer fixation. In the present study we investigated whether the appearance of 13CO2 during a separate infusion of [1,2-13C]acetate could be used for correction of [U-13C]palmitate oxidation rates in studies lasting <2 h and we quantified the appearance of tracer in the glutamine, glutamate and glucose pools of the body. 2. An infusion of either [1,2-13C]acetate (0.104 micromol min-1 kg-1) or [U-13C]palmitate (0.013 micromol min-1 kg-1) was given to eight male subjects and continued for 2 h at rest. In six subjects the infusion of [1,2-13C]acetate was repeated to determine reproducibility of the acetate recovery. 3. Fractional recovery in breath from [1,2-13C]acetate gradually increased during the infusion period at rest from 14.1 +/- 0.6% at 60 min to 26.5 +/- 0.5% at 120 min after the start of the infusion. Intersubject coefficient of variance was 8.3 +/- 0.6% and intrasubject coefficient of variance of the acetate recovery tests was 4.0 +/- 1.5%. After 2 h of [1,2-13C]acetate infusion, 12.4 +/- 0.8 and 10.3 +/- 0.9% of infused 13C was incorporated in the glutamine and glutamate pools, respectively. 4. In conclusion, the [1,2-13C]acetate recovery factor can be used for correcting the rate of [U-13C]palmitate oxidation in infusing studies of 2 h in resting conditions. Failure to use this recovery factor leads to a substantial underestimation of the rate of plasma free fatty acid oxidation. The extent of label fixation could largely be explained by accumulation of tracer carbon in glutamine and glutamate, and the accumulation in glucose is negligible.

Acetates↗

PubMed1983

Effect of variation in caries diagnosis and degree of caries on treatment decisions by dental teachers using bitewing radiographs.

Nine teachers of clinical dentistry were presented with 12 pairs of duplicated bitewings on four different occasions. At the first two examinations they indicated the presence of caries in need of treatment and at the second two the degree of caries. The diagnostic sessions were repeated to measure reproducibility. A norm for the validity of degree of enamel caries and for the estimation of specificity and sensitivity of the diagnostic categories was applied. The teachers saw on average less caries and less deep caries than the norm. Variability by the teachers was especially large between examinations for enamel lesion categories. There was a mean of 69% agreement by the teachers with their own treatment indication criteria. Over recording of treatment need (mean 19%, SD 20%) and under recording (mean 36%, SD 17%) occurred at the same viewing periods. Using Cohen's kappa, it was found that despite their variation and inaccuracy this group of teachers should select caries in dentin as the teaching criterion for treatment need. It is suggested that the sensitivity and specificity with which dental practitioners can use a criterion should be taken into account firstly when selecting it, and secondly when choosing the frequency of radiographic screening.

Adolescent↗

PubMed1982

Observations on the Object Learning Test of the Kendrick Battery for the Detection of Dementia.

This paper examines some shortcomings in the design and validation of the Object Learning Test of the Kendrick Battery. Certain issues which are important to ensure standardized administration of the test have not been considered, and the scoring procedures penalize some correct responses. Line drawings on the cards are occasionally ambiguous, and some of the repeat drawings are reproduced with unnecessary alterations. The parallel forms of the test are not matched for word frequency of the names of the objects. Questions are raised concerning the cut-off point for ascribing dementia and the statements of confidence in test diagnosis.

Dementia↗

PubMed1978

Comparison of bacteriophage typing, serotyping, and biotyping as aids in epidemiological surveillance of Klebsiella infections.

Bacteriophage typing was used to subdivide Klebsiella obtained from patients in a surgical intensive care unit during a 2-year period. The 15 phages employed to type the strains were propagated by a soft-agar layer technique. In all, 23 phage types were found among the 120 clinical strains. The phage types of repeat isolates were reproducible. Only 70% of the strains tested were phage typable, but when used in conjunction with capsular serotyping and biotyping, a much greater subdivision of the Klebsiella strains was achieved. The addition of phage typing to serobiotyping for epidemiological analysis suggested that the number of cross-infecting Klebsiella strains in the intensive care unit was few, but that these strains persisted in the unit for long periods of time and could infect different body sites.

Bacteriophage Typing↗

PubMed1994

Measurement of hand bone mineral content by dual energy x-ray absorptiometry: development of the method, and its application in normal volunteers and in patients with rheumatoid arthritis.

OBJECTIVES--To develop a method of measuring hand bone mineral content (BMC) by dual energy x ray absorptiometry (DXA); to apply this method of measuring hand BMC to normal volunteers to ascertain causes of variability; and to measure hand BMC in patients with rheumatoid arthritis (RA) of varying duration and severity. METHODS--The x ray beam of the Hologic QDR 1000 dual energy x ray absorptiometer was hardened by introducing a perspex-aluminium plate and the analysis software altered to allow for the small tissue bulk of the hand compared with the torso. Ninety five volunteers (46 men age 24-81 and 49 women age 20-83) had scans of both hands. Eight volunteers were assessed repeatedly to establish reproducibility and effect of hand position. Fifty six patients (22 men, 34 women, age range 25-86 years) with RA of differing duration and severity, had hand BMC measurement by DXA. RESULTS--The precision of BMC measurement was 2.3% with no additional variation due to hand position. Hand dominance had no significant effect on BMC. In men, hand BMC correlated with height (r = 0.57, p < 0.0001), weight (r = 0.58, p < 0.0001), forearm span (r = 0.5, p = 0.0006) and hand volume (r = 0.66, p < 0.0001). In women hand BMC correlated with height (r = 0.66, p < 0.0001), weight (r = 0.4, p = 0.003), forearm span (r = 0.3, p = 0.03) and hand volume (r = 0.49, p = 0.0008). After correcting for all these variables, male volunteers had significantly higher hand BMC than female volunteers (p = 0.01) and patients with RA had lower hand BMC than normal volunteers (total hand BMC in male volunteers 90.9 gms, 95% CI 86.9-95, in male patients 81.7 gms, 95% CI 73.7-89.6, p < 0.004, total hand BMC in female volunteers 62.2 gms 95% CI 59.8-64.5, female patients 52.3 gms, 95% CI 48.1-56.5, p < 0.005). In patients with RA, the hand BMC showed an inverse correlation with age (r = -0.44, p = 0.01), disease duration (r = -0.62, p = 0.0003), Larsen's grades (r = -0.62, p = 0.0002) and modified Sharp's method score (r = -0.69, p < 0.0001) in female patients only. CONCLUSIONS--A new, sensitive and reproducible technique of measurement of hand bone mineral content by DXA, has been developed and this method has been applied to normal volunteers and patients with RA. Hand dominance had no significant effect on hand BMC. After correcting for physical size, men have higher hand BMC than women. Hand BMC inversely correlates in women patients with disease duration and other validated methods of assessing radiological outcome in RA. Longitudinal studies are needed to establish its role in monitoring disease progression.

Absorptiometry, Photon↗

PubMed1987

A measure of quality of life for clinical trials in chronic lung disease.

Since the relationships between pulmonary function, exercise capacity, and functional state or quality of life are generally weak, a self report questionnaire has been developed to determine the effect of treatment on quality of life in clinical trials. One hundred patients with chronic airflow limitation were asked how their quality of life was affected by their illness, and how important their symptoms and limitations were. The most frequent and important items were used to construct a questionnaire evaluating four dimensions: dyspnoea, fatigue, emotional function, and the patient's feeling of control over the disease (mastery). Reproducibility, tested by repeated administration to patients in a stable condition, was excellent: the coefficient of variation was less than 12% for all four dimensions. Responsiveness (sensitivity to change) was tested by administering the questionnaire to 13 patients before and after optimisation of their drug treatment and to another 28 before and after participation in a respiratory rehabilitation programme. In both cases large, statistically significant improvements in all four dimensions were noted. Changes in questionnaire score were correlated with changes in spirometric values, exercise capacity, and patients' and physicians' global ratings. Thus it has been shown that the questionnaire is precise, valid, and responsive. It can therefore serve as a useful disease specific measure of quality of life for clinical trials.

Clinical Trials as Topic↗