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Results for “Repeatability and Reproducibility”

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PubMed1978

Reproducibility and comparative analysis of repeated intravenous and oral glucose tolerance tests.

We have developed a methodology for measuring the reproducibility of the oral glucose tolerance test (OGTT) and the intravenous glucose tolerance test (IVGTT) in normal subjects and in offspring of conjugal diabetic parents. Both groups of subjects revealed more striking correlations of several parameters of blood glucose and insulin secretion between two IVGTTs than between two OGTTs. Employing arbitrary criteria, we calculated a "reproducibility index" as a quantitative measure of blood glucose variability in each subject. No significant difference was found in the reproducibility of OGTT versus IVGTT, nor in normals versus the offspring. Only about 50 per cent of the tests in normals and in the offspring could be considered to be "reproducible." The offspring revealed greater correlations of several parameters, particularly insulin secretion, between the two IVGTTs and between the two OGTTs as compared with the normal group. However, the blood glucose variations tended to be considerably greater in the offspring from one to the other test.

Administration, Oral↗

PubMed1987

Gastric acid secretory capacity falls after repeated within-day pentagastrin testing in fed subjects.

Between-day pentagastrin testing yields highly reproducible stimulated gastric acid output values, but little is known of the reproducibility of repeated within-day pentagastrin tests. We have performed three pentagastrin tests within the 1 day in nine healthy subjects. Within-day tests were 6 hours apart; the first followed an overnight fast and the second and third were both 4 hours after a substantial meal. A further test was performed the following morning, again after an overnight fast, which allowed comparison of within-day and between-day testing. In the second and third within-day tests there was a marked decrease of stimulated gastric acid output, with both maximal and peak acid output decreased to approximately half of the value of the first test (P less than 0.01). By contrast there were no significant differences in the acid output values obtained in between-day tests (both following an overnight fast). Possible mechanisms for the decreased output on repeated within-day testing include alterations in the sensitivity of the gastrin receptor, or some neurohumoral influence secondary to the preceding meal. Future studies of the duration of action of drugs affecting acid secretion may need to take account of these findings.

Adult↗

PubMed1988

Collaborative evaluation in seven laboratories of a standardized micromethod for yeast susceptibility testing.

The new micromethod for yeast susceptibility testing, MYCOTOTAL, was evaluated with 10 reference strains in seven laboratories. Ready-to-use microtitration plates and the same synthetic medium were used with two dilutions of imidazoles, flucytosine, and amphotericin B, permitting the categorization of each strain as susceptible, intermediate, or resistant. The results were compared with the MIC for each reference strain, and the repeatability and reproducibility were evaluated. The yeasts tested presenting different patterns of susceptibilities in reference MICs included six strains of Candida albicans, two strains of Candida tropicalis, one strain of Candida parapsilosis, and one strain of Torulopsis glabrata. For 4,200 antifungal agent-yeast results, the repeatability was 99.3% and the reproducibility was 96.3%. The correlation between the reference MICs and the category results was 91.5% for seven laboratories (and 92.7% for six laboratories excluding the laboratory which did not follow exactly the same protocol). We observed only 7.9% minor discrepancies, 0.5% (0.29% for six laboratories) major discrepancies, and 0.1% uninterpretable results. The percentages of concording results were similar for each strain and each antifungal agent tested. The overall results indicated that MYCOTOTAL was a reliable and reproducible method, well correlated with reference MICs. This ready-to-use micromethod with the same medium for all antifungal agents would be an important step in the necessary standardization of yeast susceptibility testing.

Antifungal Agents↗

PubMed1992

Non-modulation as an intermediate phenotype in essential hypertension.

Non-modulation is a trait characterized by abnormal angiotensin-mediated control of aldosterone release and the renal blood supply. To determine whether non-modulation defines a specific subgroup of the hypertensive population and its utility as an intermediate phenotype, we have studied the distribution of this quantitative trait, whether its features are reproducible on repeated testing, and whether there is concordance of its multiple features. Essential hypertensive patients (224) and normotensive subjects (119) received an infusion of angiotensin II (Ang II) at 3 ng.kg-1.min-1 for 30-45 minutes. p-Aminohippurate (PAH) clearance was assessed as an index of renal plasma flow while the subjects were on a 200 meq sodium diet; plasma aldosterone levels were measured while the subjects were on a 10 meq sodium diet. In 54 subjects, diuretic-induced volume depletion superimposed on a low salt diet was substituted for the Ang II infusion. The results of each study were submitted to maximum likelihood analysis to assess bimodality. In response to both diuretic-induced volume depletion (p < 0.000023) and Ang II infusion (p < 0.0009), aldosterone responses were bimodally distributed in the essential hypertensive but not in the normotensive subjects, suggesting that this trait identifies a discrete subgroup. In the 59 subjects who had both an adrenal and renal study, 50 (85%) were concordant. Finally, in 27 subjects studied two to six times over a span of 1-60 months, the intraclass correlations of the adrenal, PAH, or both responses were highly significant (p values between 0.001 and 0.00007), indicating high reproducibility of results on repeated testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗

PubMedDate not supplied

Mechanism of thrombin-induced endothelium-dependent coronary vasodilation in dogs: role of its proteolytic enzymatic activity.

We have recently reported that exogenous thrombin produced a dose- and endothelium-dependent coronary vasodilation in both intact open-chested dogs and in isolated dog coronary artery preparations. To determine whether the observed vasodilatory effect may be related to thrombin proteolytic enzymatic activity, effects of other proteases, such as trypsin, chymotrypsin, and pepsin, on the mechanical responses of isolated dog coronary arteries were studied. Among the four proteases evaluated, only thrombin (0.01-0.1 U/ml) and trypsin (0.03-0.67 U/ml) consistently produced a potent dose- and endothelium-dependent relaxation, that was reproducible with repeated testings. Addition of chymotrypsin (0.01-1.0 U/ml) produced only a minimal effect and was not reproducible, while addition of pepsin, as much as 10 U/ml, did not produce any effect. The specific soybean trypsin inhibitor and aprotinin, but not heparin and hirudin, competitively shifted the trypsin dose-response to the right, whereas heparin, hirudin, and antithrombin III proved to be more effective than trypsin inhibitors in inhibiting the thrombin-induced vasodilation. In all cases, the thrombin- and trypsin-induced vasodilation were equally sensitive to inhibition by the specific synthetic thrombin inhibitor, PPACK (D-phenylalanyl-L-propyl-L-arginine chloromethyl ketone, 1-30 nM). PPACK, however, had no effect on the other endothelium-dependent coronary vasodilators, such as acetylcholine and adenosine triphosphate, in our isolated dog coronary artery preparations. Biochemical determinations of the amidolytic activity of thrombin, using Tosylglycyl-L-prolyl-L-arginine-p-nitroanilide as a chromogen, also indicated a similar PPACK and heparin-antithrombin III dose-dependent inhibition of the thrombin enzymatic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Chloromethyl Ketones↗

PubMed1992

The influence of ambulatory blood pressure monitoring on the design and interpretation of trials in hypertension.

OBJECTIVE: To describe the reproducibility of diastolic blood pressure (DBP) measurement by clinic and ambulatory monitoring and to evaluate the effects of this reproducibility on the design and interpretation of clinical trials in hypertension research. DESIGN: Prospective single-blind study of repeat measurement reproducibility of blood pressure recording. SETTING: Tertiary referral hospital hypertension clinic. PATIENTS: One hundred untreated mild-to-moderate hypertensive subjects taking 1 month of single-blind placebo. MAIN OUTCOME MEASURES: A single clinic measurement of DBP was poorly reproducible and the results for single DBP estimates taken out of a daytime ambulatory recording were similar. Average ambulatory DBP was much more reproducible, although this improvement depended upon the averaging of many measurements taken throughout the day. CONCLUSIONS: Ambulatory monitoring would decrease antihypertensive trial size by a factor of four or halve the size of detectable DBP difference between treatments. The use of poorly reproducible DBP measurements such as single clinic readings may have led to an underestimation of the risks of minor degrees of blood pressure elevation because of a 'regression dilution' bias. For single clinic DBP readings, we calculate this underestimation to be as much as 69%, and for average ambulatory DBP approximately 20%.

Adult↗

PubMed1991

Time-dependent variation in the cardiac conduction system assessed in young healthy individuals at weeks' interval: implications for clinical trials.

The time-dependent physiologic variations of the cardiac conduction system were evaluated at repeated invasive studies in 10 healthy individuals. Their mean age was 28 years (range 22 to 34) and they volunteered to undergo two electrophysiologic studies at intervals of 14 to 63 days (mean 25). The coefficients of variation, repeatability and reproducibility, which should be the preferred statistics when assessing the reproducibility of continuous variables, were calculated. The mean sinus cycle length had a high reproducibility, with coefficients of variation between 2% and 6%. The mean and maximal sinus node recovery times, however, varied considerably. The reproducibility was very high for ventricular depolarization and repolarization (QRS, JT, QT), with coefficients of variation between 2% and 6%. The coefficients of variation were below the acceptable 10% value for intraatrial conduction, atrioventricular (AV) node conduction, His-Purkinje conduction as well as the Wenckebach point; for the effective refractory period of the AV node, it was 12%. Repeat invasive electrophysiologic testing is a safe and reproducible method for evaluating and comparing cardioactive drug effects in healthy subjects. The same statistical analyses were applied to previously published studies on continuous electrophysiologic variables, which allowed comparisons among different groups of healthy and sick persons, as well as among different electrophysiologic variables and procedures. Furthermore, the minimal actual treatment differences that can be detected with a reasonable (80%) probability at a predetermined (5%) significance level using a crossover design were estimated for different electrophysiologic variables. These data will assist in the calculation of the necessary sample size for clinical trials and related purposes.

Adult↗

PubMed1992

Evaluation of human diaphragm contractility using mouth pressure twitches.

Mouth (PmT), esophageal (PesT), and transdiaphragmatic pressure twitches (PdiT) in response to single supramaximal bilateral phrenic nerve shocks were recorded during relaxation between total lung capacity (TLC) and functional residual capacity (FRC) in five normal volunteers. The PmT versus PesT or PmT versus PdiT relationships, which were linearly correlated (all r greater than 0.76), were not affected by diaphragm fatigue and were reproducible on repeated determinations over a period exceeding 1 yr. The PmT versus lung volume relationship was also linear (all r greater than 0.72) and reproducible, and its changes following diaphragm fatigue reliably reflected the changes in diaphragm contractility. We conclude that PmT is a reliable measure of diaphragm pressure-generating capacity in normal individuals and has the potential of providing similar information in patients.

Adult↗

PubMed1991

[Problems of the reproducibility of the inhaled dosage exemplified with the Pari provocation test I apparatus].

The unspecific bronchial provocation test--usually performed with histamine, metacholine or carbachol--is used to determine whether bronchial hyperreactivity is present, and to what degree. Epidemiological studies have shown, that an overlap exists between "healthy" and "sick". There are several reasons for this, the most important being the insufficient reproducibility of intrabronchial deposition and the fact that the total provocation dose is often unknown. The following factors must be taken into account to improve this situation: 1. Only those devices where the particle spectrum is not influenced by the inspiration flow (without additional airstream) should be used to produce aerosols. 2. The air current containing aerosols is vapour saturated when liquid aerosols are produced. As the vapour is derived from the nebulizing solution it forms part of the weight or volume loss, this can be up to 50% of the total weight/volume loss. The aerosol output is far more constant and practically independent of the vapour saturation and the temperature. The intrabronchial dose can therefore not be calculated according to the weight loss of the nebulizer, as this is incorrect. 3. The evaporation of the nebulizing solution leads to an increase in the concentration of the test substance, especially towards the end of the evaporation process. Thus, the volume of the nebulizing solution should always be as large as possible or renewed early. 4. The slower the inhalation maneuver, the less the reproducibility of the intrabronchial deposition is impaired. The intrabronchial deposition varies least, when a slow inspiratory vital capacity maneuver is carried out (inspiration time greater than 8 s). Exhalation should be normal or even rapid, as aerosol deposition is thus increased, due to airway collapse. Breath-holding at the end of inspiration, for about 3-4 seconds, is favourable. 5. The anatomy of the glottic region varies greatly interindividually, influencing intrabronchial deposition. To reduce this to a minimum, the average diameter of the particles should not exceed 2 microns. On the other hand, the diameter of particles should not be under 1 micron, as the inhaled amount of substance is then markedly reduced (volume approximately d3). 6. Reservoirs, storaging the aerosol before inhalation, increase reproducibility, since they stabilize the aerosol due to vapour saturation. Plastic reservoirs must either be of antistatic material, or made antistatic by being filled repeatedly. The reproducibility of intrabronchial deposition is in the range of +/- 15% for the PARI-Provokationstest device I, (determined by radioactive labelling).(ABSTRACT TRUNCATED AT 400 WORDS)

Aerosols↗

PubMed1991

[Validation of an ultrasonographic method of gastric emptying measurement in men].

Our purpose was to validate an ultrasonographic technique based on the assessment of the gastric antrum. Sixteen patients presenting with various functional disorders were studied by ultrasound on two occasions. Ten healthy volunteers were simultaneously studied by scinti- and ultrasonic scans. After an overnight fast, the healthy subjects ingested a 2,000 kJ test meal containing 150 microCi of 111In DTPA in 250 ml orange juice and 3 mCi of 99m Tc sulfur colloid in chicken liver. Using an ultrasound scanner fitted with a 3.5 MHz transducer, the area of the gastric antrum section was always measured in the same plane. Ultrasonographic measurement of gastric emptying rate was feasible in all of the 10 healthy subjects and in 14 of 16 selected patients. The ultrasonographic method was reproducible, and repeated t 1/2 measurements in 14 patients correlated well (95.3 +/- 27.9 vs 99.2 +/- 20.6 min; r = 0.70, P less than 0.001). The t 1/2 measurement was 39.4 +/- 7.7 min with the ultrasonographic method, and correlated well with 36.4 +/- 4.3 min for the t 1/2 measurement of the liquid phase with the scintigraphic method. We conclude that the ultrasonic method was reproducible and could be used for assessment of gastric emptying rate when repeated measurements are necessary, especially in pharmacologic studies.

Adult↗

PubMed1976

Human cell-mediated cytotoxicity estimated by lymphocyte titration.

Human lymphocyte immunity to tumor-derived target cells was estimated by titrating lymphocyte concentration to achieve a 50% reduction of target cell survival. This lymphocyte titration assay gave estimates of cytotoxicity that were different from those obtained with the conventional cell-mediated cytotoxicity assays but were more proportional to lymphocyte activity. Estimates of cytotoxicity obtained using the lymphocyte titration assay were reproducible upon repeated testin over the course of several months and were relatively unaffected by two- to fourfold variations in target cell concentration. Target cell-specific cytotoxicity was reproducible but often did not appear to be tumor specific.

Antibody Formation↗

PubMed1989

Reproducibility of microscopic and cultural data in repeated subgingival plaque samples.

In association studies, micro-organisms can only be recognized as suspects for playing a major rôle in the development of a pathological environment, if their destructive action goes along with a marked proportional increase of their numbers or if their first detection can be related to the clinical onset of the disease. Limitations in the reproducibility of repeated samples have to be taken into account, when changes of the microbial composition of subgingival environments are to be studied, and when local clinical changes are to be related to shifts in the composition of the pertaining microbiological compartment. To study reproducibility, a total of 109 sites was sampled repeatedly with sterile paperpoints at an interval of 7 to 10 days in 24 patients suffering from periodontal disease and 12 edentulous patients wearing successful and failing osseointegrated titanium implants. Using continuous anaerobic techniques, the samples were cultured on nonselective and selective media and were studied by darkfield microscopy. Both the intertest-agreements of frequencies of detection (kappa-statistics) as well as the discrepancies of proportions of bacterial groups and selected bacterial species were determined. The standard deviation of proportional differences between first and second samples ranged between 6.4% (fusiform organisms) and 17.2% (coccoid cells) for darkfield parameters, between 4.3% (B. melaninogenicus on ETSA/Kana.) and 14.0% (B. gingivalis on ETSA/Kana.) for selected bacterial species and between 6.9% (gram-negative anaerobic cocci) and 24.0% (gram-positive facultative cocci) for bacterial groups classified according to gram stain characteristics and atmospheric growth conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗

PubMed1985

Assessment of transdiaphragmatic pressure in humans.

Maximal force developed by the diaphragm at functional residual capacity is a useful index to establish muscle weakness; however, great disparity in its reproducibility can be observed among reports in the literature. We evaluated five maneuvers to measure maximal transdiaphragmatic pressure (Pdimax) in order to establish best reproducibility and value. Thirty-five naïve subjects, including 10 normal subjects (group 1), 12 patients with chronic obstructive pulmonary disease (group 2), and 13 patients with restrictive pulmonary disease (group 3), were studied. Each subject performed five separate maneuvers in random order that were repeated until reproducible values were obtained. The maneuvers were Mueller with (A) and without mouthpiece (B), abdominal expulsive effort with open glottis (C), two-step (maneuver C combined with Mueller effort) (D), and feedback [two-step with visual feedback of pleural (Ppl) and abdominal (Pab) pressure] (E). The greatest reproducible Pdimax values were obtained with maneuver E (P less than 0.01) (group 1: 180 +/- 14 cmH2O). The second best maneuvers were A, B, and D (group 1: 154 +/- 25 cmH2O). Maneuver C produced the lowest values. For all maneuvers, group 1 produced higher values than groups 2 and 3 (P less than 0.001), which were similar. The Ppl to Pdi ratio was 0.6 in maneuvers A and B, 0.4 in D and E, and 0.2 in C. We conclude that visual feedback of Ppl and Pab helped the subjects to elicit maximal diaphragmatic effort in a reproducible fashion. It is likely that the great variability of values in Pdimax previously reported are the result of inadequate techniques.

Abdominal Muscles↗

PubMed1987

Human Fc gamma receptors: stable inter-donor variation in quantitative expression on platelets correlates with functional responses.

Evidence has recently been presented that a 40,000 dalton membrane sialoglycoprotein (p40) shared by monocytes and granulocytes serves as the human platelet receptor for aggregated IgG. We now report that the platelets of normal donors exhibit stable quantitative differences in the expression of this receptor molecule, as determined by flow cytometry using fluorescent staining with murine monoclonal antibody to p40 (mab IV.3). These inter-donor differences were reproducible on repeated testing over at least 4 mo. In concurrent assays, the binding of mab IV.3 to each donor's platelets was highly correlated with the binding of heat-aggregated human IgG, also assayed by flow cytometry. The biological relevance of this quantitative variation in IV.3 binding is suggested by its reproducible correlation with platelet responsiveness to aggregated IgG measured by aggregometry. Such stable quantitative variation in platelet Fc receptor expression among individual humans could contribute to differences in severity of certain pathologic processes initiated by IgG-containing immune complexes.

Antibodies, Monoclonal↗

PubMed1990

Quantitative chamber angle measurement utilizing image-processing techniques.

An image-processing technique was applied to the measurement of the anterior chamber angle. The anterior eye segment was documented by a new instrument, named anterior eye segment analysis system for biometry of the anterior eye segment. The approximated curve of the corneal posterior curvature and the line tangent to the anterior surface of the iris were calculated as the anterior chamber angle. The mean error of the reproducibility of repeated measurements for the same image was 1.6 +/- 0.81% and that of 3 images of the same eye which were taken at 3 different times was within 5.2%.

Adult↗

PubMed1988

Reproducibility of CT bone densitometry: operator versus automated ROI definition.

Intrasubject reproducibility with repeated determination of vertebral mineral density from a given set of CT images was investigated. The region of interest (ROI) in 10 patient scans was selected by four independent operators either manually or with an automated procedure separating cortical and spongeous bone, the operators being requested to interact in ROI selection. The mean intrasubject variation was found to be much lower with the automated process (0.3 to 0.6%) than with the conventional method (2.5 to 5.2%). In a second study, 10 patients were examined twice to determine the reproducibility of CT slice selection by the operator. The errors were of the same order of magnitude as in ROI selection.

Algorithms↗

PubMedDate not supplied

Liquid chromatographic method for multiresidue determination of benzimidazoles in beef liver and muscle: collaborative study.

A liquid chromatographic method for determination of thiabendazole, 5-hydroxythiabendazole, oxfendazole, mebendazole (MBZ), and fenbendazole (FBZ) in cattle liver and muscle was collaboratively studied in 7 laboratories in 1986. For blind fortified samples containing 800 ppb FBZ, average recovery and relative standard deviations for repeatability and reproducibility (RSDr and RSDR) based on results from 6 of the participating laboratories were 83%, 12.7%, and 14.0%, respectively. Recoveries of FBZ from incurred liver samples were more variable. Recoveries of MBZ from livers fortified at the 100 ppb level were encouraging; however, the drug levels were too low in the incurred samples used for MBZ studies. Except for FBZ and MBZ in liver, the study data were not satisfactory. The method has been adopted official first action by AOAC for determination of 800-1600 ppb fenbendazole in liver. The analysis should be repeated using a smaller sample size when initial analyses show levels greater than 1600 ppb FBZ.

Animals↗

PubMed1989

Efficiency of the respiratory muscles in healthy individuals.

We evaluated respiratory muscle performance by determining the energy cost of breathing against incremental threshold loads and calculating the efficiency of the respiratory apparatus for handling the added work. In five subjects, the energy cost of breathing against the loads, and thus the calculated efficiency of the respiratory muscles, was reproducible on repeated measurements. In all subjects, the calculated efficiency varied while breathing with low loads but was relatively constant at loads that resulted in a mouth pressure of 20 to 60% of the subjects' maximal static inspiratory pressure (PImax). The mean efficiency calculated between 20 to 60% of PImax in 30 normal subjects (15 males and 15 females) ranged between 1.54 and 7.98%. It was significantly greater in males (5.41 +/- 0.43%) (mean +/- SEM) than in females (2.41 +/- 0.17%). There was no relationship between efficiency and body size, but the efficiency correlated with inspiratory muscle strength (PImax). We suggest that measurement of the efficiency of the respiratory muscles over a spectrum of incremental threshold loads is a simple, noninvasive, and reproducible method of assessing respiratory muscle performance and may have clinical application.

Adolescent↗