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Results for “Repeatability and Reproducibility”

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PubMed1998

An evaluation of RAPD fragment reproducibility and nature.

Random amplified polymorphic DNA (RAPD) fragment reproducibility was assayed in three animal species: red deer (Cervus elaphus), wild boar (Sus scrofa) and fruit fly (Drosophila melanogaster). Ten 10-mer primers (Operon) were tested in two replicate reactions per individual under different stringency conditions (annealing temperatures of 35 degrees C or 45 degrees C). Two estimates were generated from the data: autosimilarity, which tests the reproducibility of overall banding patterns, and band repeatability, which tests the reproducibility of specific bands. Autosimilarity (the similarity of individuals with themselves) was lower than 1 for all three species ranging between values of 0.66 for Drosophila at 45 degrees C and 0.88 for wild boar at 35 degrees C. Band repeatability was estimated as the proportion of individuals showing homologous bands in both replicates. The fraction of repeatable bands was 23% for deer, 36% for boar and 26% for fruit fly, all at an annealing temperature of 35 degrees C. Raising the annealing temperature did not improve repeatability. Phage lambda DNA was subjected to amplification and the pattern of bands compared with theoretical expectations based on nucleotide sequence. Observed fragments could not be related to expected ones, even if a 2 bp mismatch is allowed. Therefore, the nature of genetic variation uncovered by the RAPD method is unclear. These data demonstrate that prudence should guide inferences about population structure and nucleotide divergence based on RAPD markers.

Animals↗

PubMed1996

Effect of applanation tonometry on mean corneal curvature.

PURPOSE: To evaluate whether applanation tonometry affects corneal curvature and if so, the implications for intraocular lens power calculation. SETTING: Birmingham and Midland Eye Hospital, Birmingham, England. METHODS: Twenty-two patients attending the preoperative assessment clinic were enrolled in the study. Keratometry was performed immediately before, 1 minute after, and 10 minutes after standard Goldmann tonometry. Main outcome measures were mean corneal refractive power and its reproducibility (coefficient of repeatability). RESULTS: No clinically significant difference was noted between preapplanation and postapplanation readings (P = .6), and reproducibility was not significantly affected. CONCLUSION: The results indicate that corneal applanation before keratometry does not compromise the prediction of postoperative refraction.

Aged↗

PubMed1999

Sequence variation and evolution of the mitochondrial DNA control region in the musk shrew, Suncus murinus.

The complete mitochondrial DNA (mtDNA) control region was cloned and sequenced in the musk shrew, Suncus murinus, Insectivora. The general aspect was similar to that found in other mammals. We have found in two locations of this region the presence of arrays of tandem repeats like those in other shrew species. One array was located in the left domain containing the termination-associated sequences (TAS) and the length of a copy was 77 bp. The other repeats were situated upstream from the recognition site for the end of H-strand replication in the right domain and were 20 bp long. The left halves of the control region containing the former repeats were sequenced and compared in several laboratory lines and wild animals from different localities, variations in copy number of repeated sequences were found both among individuals and within an individual. A comparative study of repeated sequences provides useful indication for the origin and evolution of tandem repeated sequences. Strand slippage and mispairing during replication of mtDNA with concerted manner is currently regarded as a dominant theory to account molecular mechanism for tandemly repeated sequences, and the pattern of sequence and length variation in our study supports this theory. Our results, however, suggest that the evolution of the repeated sequences containing the TAS in the musk shrew might go through the process of two steps; at the first step one complete repeated and several incomplete repeated sequences had reproduced in common ancestor of the shrew, and the second stage step-up of complete repeated sequences occurred with concerted evolution after differentiation into continental and insular groups.

Animals↗

PubMed2006

Nickel quantification in serum by a validated sector-field inductively coupled plasma mass spectrometry method: Assessment of tentative reference values for an Italian population.

The daily exposure to Ni from food, industrial processes, jewellery and coins makes the determination of Ni in human serum an important way to monitor the health status in non-occupationally exposed subjects. To this end, a method based on sector-field inductively coupled plasma mass spectrometry was developed and validated. The limits of detection (LoD) and quantification (LoQ), sensitivity, linearity range, trueness, repeatability, within-laboratory reproducibility and robustness were the considered issues of the validation process. The uncertainty associated with the measurements was also calculated, according to the Eurachem/Citac Guide. The method LoD and LoQ were 0.03 and 0.09 ng mL(-1), linearity was over two order of magnitude, trueness was -3.57%, and the repeatability and reproducibility showed relative standard deviations equal to 4.56% and 6.52%, respectively. The relative expanded uncertainty was 21.8% at the Ni levels found in the general population. The tentative reference value for serum Ni was 0.466 +/- 0.160 ng mL(-1) with a related interval between 0.226 and 1.026 ng mL(-1).

Adult↗

PubMed2001

Lessons from the post coronary artery bypass graft study in evaluating and controlling technical variability in angiographic trials. Post CABG Investigators.

Although many investigators have evaluated the technical variability of quantitative angiographic techniques used to study atherosclerosis regression in native coronary arteries, few have studied the variability inherent in repeated studies of atherosclerotic saphenous vein grafts. This study describes 2 studies performed during the course of the Post Coronary Artery Bypass Graft (CABG) Clinical Trial that were designed to assess the reproducibility of: (1) repeated angiographic views within a short time period; and (2) reproducibility of the total process of quantitative analysis of saphenous vein graft angiograms. Statistical methods are described that provide a more meaningful assessment of the impact of measurement variability in the analytic process versus the variability related to changes induced by pharmacologic interventions. One such method, the increase in standard deviation (SD) among patients (ISDP), showed that repeated angiographic views increased the variability of calculation of lesion minimal diameter by 1.5%, whereas the ISDP for repetition of the entire process of quantitative angiographic readings increased variability 6.4%. These data from the Post CABG trial reveal that technical variability is small and has negligible impact on the conclusions of the study.

Coronary Angiography↗

PubMed2000

Intraesophageal acid perfusion sensitizes the esophagus to mechanical distension: a Barostat study.

OBJECTIVE: The pathogenesis of noncardiac chest pain is unclear. Increased gastroesophageal reflux and decreased pain thresholds to intraesophageal balloon distension have been demonstrated in a proportion of such patients. We aimed to investigate whether acid exposure sensitizes esophageal mechanoreceptors in healthy volunteers. METHODS: After an overnight fast, an infinitely compliant balloon, 4.5 cm in length and mounted on a multilumen transnasal manometry catheter, was placed 8.5 cm above the lower esophageal sphincter in 12 healthy male volunteers aged 18-39 yr. After determination of the minimal distending pressure, the balloon was inflated up to 48 mm Hg by means of a computer-controlled barostat (G & J Electronics, Canada). Graded stepwise distensions were interspersed with random decreases in pressure to two-thirds of the previous value. At each pressure level, the subjects were asked to report on sensation and the presence of pain. Baseline distension was repeated to determine reproducibility of the pressure/volume relationship and also the perception and pain thresholds. After the baseline distension sequence, the esophagus was perfused for 20 min (at 7 ml/min) with either normal saline (control) or 0.1 N hydrochloric acid at 37 degrees C on a random basis. RESULTS: Basal sensory thresholds varied widely (first perception 5-36 mm Hg, pain 8 > or = 43 mm Hg). Two subjects did not experience pain up to the maximum distending pressure (42 and 43 mm Hg, respectively, after correction for the minimal distending pressure). Esophageal body compliance was similar on repeat distension. Sensory thresholds were reproducible with different distensions (perception r = 0.99, pain r = 0.95). Saline resulted in no significant changes in perception or pain thresholds. Acid perfusion reduced first perception (median before and after acid, 15 mm Hg and 8 mm Hg, respectively, p = 0.05) and pain threshold (median before and after acid, 32.5 mm Hg and 26.5 mm Hg, respectively, p = 0.05). When compared to changes after saline perfusion, acid perfusion reduced the perception threshold (median change, -3.8 mm Hg vs 0 mm Hg, p = 0.04) and tended to reduce the pain threshold (median change, -3.75 mm Hg vs +0.75 mm Hg, p = 0.09). CONCLUSIONS: Intraesophageal balloon distension using a barostat is a reproducible method of measuring esophageal body compliance and sensory thresholds. Acute exposure to acid seems to sensitize the esophagus to perception from intraluminal balloon distension.

Adolescent↗

PubMed2005

Objective growth monitoring of the maxilla in full term infants.

OBJECTIVE: To develop a non-invasive method for longitudinal maxillary volume measurements and to provide first normative data. DESIGN: Thirty-four healthy infants served as a gold standard for a growing population sample. Alginate impressions were taken of the upper jaw within the first week after birth, and consecutively at different stages of development. The plaster casts were digitised by an optical scanner generating a high resolution polygon mesh of each object. The digital models were aligned to a reference coordinate system with an iterative, landmark-independent procedure. Biometric linear and volume measurements were obtained by using feature-dependent calculations independent of landmark placements. Intra-investigator reproducibility was tested by repeated alignments and measurements of 30 randomly selected casts. To assess the effect of mesh resolution, the reproducibility test was repeated with low resolution models. The method was proved to be valid on the defined gold standard consisting of 96 consecutive edentulous casts. RESULTS: Feature-dependent, linear distances are less error prone (0.56-2.66%) compared to subjectively determined measurements (0.88-3.65%). The same applies to feature-dependent volume calculations (4.34%) compared to subjectively determined volumes (4.95%). Mesh resolution shows an effect (p<or=0.001) only on two linear measurements: palatal depth and palatal length. Growth of the individuals in the population sample was evidently confirmed by the maxillary volume measurements (asymptotic pattern) and by comparisons of head circumference (proportional pattern). CONCLUSION: The described method is non-invasive, precise and without any risk for the infant. Maxillary volume calculation could serve as an important biometric measurement for bone growth evaluation.

Biometry↗

PubMed1997

A comparison of sonically derived and traditional cephalometric values.

The roentgenocephalometric technique is the standard used by orthodontists to assess skeletal, dental, and soft-tissue relationships. However, this technique exposes patients to radiation, preventing orthodontists from taking frequent cephalograms to assess growth and to monitor treatment. Recently, the Dolphin Imaging Company developed the DigiGraph, a nonradiographic cephalometric method that uses sound waves and mathematical algorithms, and consequently does not expose patients to radiation. But the DigiGraph's accuracy as a cephalometric alternative has not been adequately investigated. The purpose of this study was to compare the values obtained by traditional cephalometrics with those obtained by the DigiGraph technique for 30 well-known measurements, and then to assess the repeatability (intraobserver comparison) and reproducibility (interobserver comparison) for both techniques. Eighteen of the 30 measurements had mean differences that were statistically significant (p > .0067). Regression plots generally illustrate low correlations for the measurements, although Ricketts' esthetic line (upper and lower lip) and Steiner's soft-tissue convexity reveal strong linear relationships between the two methods. Additionally, the radiographically generated measurements showed greater repeatability and reproducibility.

Adolescent↗

PubMed1996

In vivo electrochemical studies of the dynamic effects of locally applied excitatory amino acids in the striatum of the anesthetized rat.

The actions of locally applied excitatory amino acids (EAAs) on dopamine nerve terminals in the striatum of the urethane-anesthetized rat were investigated. Rapid (5 Hz) in vivo electrochemical recording was used to measure the amplitude and duration of dopamine (DA) overflow elicited by the local application of glutamate, N-methyl-D- aspartate (NMDA), kainate, quisqualate, quinolinate and DL- alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid. EAAs were pressure ejected into the striatum via a pipette positioned 300 +/- 30 mum away from the electrochemical working electrode. Brief (5s) applications of the EAA agonists directly elicited DA-like electrochemical signals with amplitudes averaging about 2 microM. In some instances, putative increases in ascorbic acid-like signals were detected. Repeated applications of glutamate agonists in the same brain site resulted in diminished electrochemical responses, compared to the complete reproducibility seen after repeated applications of 120 mM potassium. Low doses of NMDA (10 mM barrel conc), which did not cause a detectable increase in the electrochemical baseline signal, significantly potentiated (50%) potassium-evoked DA overflow. These results indicate that low levels of endogenously released glutamate may modulate overflow when DA nerve terminals are depolarized, while higher concentrations of glutamate may directly elicit increases in extracellular levels of DA and/or ascorbic acid.

Adolescent↗

PubMed2003

Determination of ursodeoxycholic acid in pharmaceutical preparations by capillary electrophoresis with indirect UV detection.

A simple and rapid capillary electrophoretic method, with indirect UV detection, for the quantification of ursodeoxycholic acid (UDCA) in pharmaceutical preparations was developed in this study. Sodium p-hydroxy benzoate was used as background electrolyte (BGE) (5 mM, pH 8.0) and visualization agent. Separation was carried out on a fused-silica capillary (50 microm x 72 cm) at a potential of 25 kV under ambient temperature and detected at 250 nm. Glycocholic acid was used as internal standard for quantification. Both run-to-run repeatability and day-to-day reproducibility of migration time were below 0.1% relative standard deviation (R.S.D.). Repeatability and reproducibility of relative peak height were 3.3 and 3.8% R.S.D., respectively. Accuracy was tested by spiking two pharmaceutical tablets with standards and the recoveries were 101.9+/-9.87 and 99.6+/-9.60% (n=3), respectively. Linearity of relative peak height was tested in the range 20-100 microg/ml. Limit of detection (LOD) was 3 microg/ml. The method could be used to assay UDCA raw materials and formulation products.

Electrophoresis, Capillary↗

PubMedDate not supplied

Liquid chromatographic determination of acetaminophen in tablets: collaborative study.

A reverse phase liquid chromatographic method previously reported for the determination of acetaminophen in tablets was collaboratively studied by 5 laboratories. Each collaborator received duplicate samples of a synthetic tablet formulation and 3 powdered commercial tablet composites. The composites represented single-component and multi-component proprietary products and a single-component generic product. The pooled repeatability (CVDo) and reproducibility (CVDx) values for the proprietary tablets were 0.89 and 1.34%, respectively. For the generic tablets, these values were 0.66 and 0.74%, respectively. The pooled recovery value for acetaminophen added to the synthetic formulation was 98.9 +/- 0.7% (n = 10) with a CV of 0.75%, CVDo of 0.37%, and CVDx of 0.78%. The overall repeatability of the method was 0.64%, and the overall reproducibility was 0.95%. The method has been adopted official first action.

Acetaminophen↗

PubMedDate not supplied

Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study.

The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen x 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, sR = 0.016, repeatability relative standard deviation (RSDr) = 1.287%, reproducibility relative standard deviation (RSDr) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

Animals↗

PubMed2001

Intraobserver and interobserver variability of transabdominal Doppler velocimetry measurements of the fetal ductus venosus between 10 and 14 weeks of gestation.

OBJECTIVE: To assess the intraobserver repeatability and interobserver reproducibility of transabdominal Doppler ultrasound measurements of ductus venosus blood flow in fetuses between 10 and 14 weeks of gestation. DESIGN: A prospective study with the following end-points: coefficient of variation, intraclass correlation coefficients within and between observers, repeatability coefficient and Cohen's kappa coefficient. SUBJECTS AND METHODS: Doppler velocimetry indices (maximum peak systolic velocity during ventricular systole, end-diastolic velocity during atrial contraction, peak systolic velocity/end-diastolic velocity ratio and pulsatility index for veins) were successfully measured three times by the same trained observer in 67 fetuses. Of these, in 24 fetuses, the measurements were then repeated by a second trained observer. In addition, both observers classified qualitatively the blood flow as being normal or abnormal with regard to the presence or absence/reversal of flow during atrial contraction. RESULTS: The intraobserver repeatability of the pulsatility index for veins measurements was considered good with a coefficient of variation of 8.9% and an intraclass correlation coefficient value of 0.62. However, inconsistencies occurred in maximum peak systolic velocity, end-diastolic velocity and systolic/diastolic ratio measurements, which had coefficients of variation of 19%, 28.5%, and 25.4%, respectively. The corresponding intraclass correlation coefficient values were 0.70, 0.69 and 0.60. Interobserver reproducibility of these indices was unsatisfactory, the coefficient of variation varying between 11.5% and 47.2% and the intraclass correlation coefficient between 0.18 and 0.44. Agreement between the repeated observations with regard to interpretation of normal or abnormal blood flow varied from moderate (interobserver) to very good (intraobserver). CONCLUSIONS: There was considerable variability in all Doppler indices except for the intraobserver repeatability of the pulsatility index for veins measurement. This makes the implementation of the semiquantitative Doppler indices in a screening setting difficult. On the contrary, qualitative classification of the flow velocity waveforms seemed to be a reproducible method.

Adolescent↗

PubMed2003

A collaborative study of a method for the enumeration of probiotic bifidobacteria in animal feed.

An enumeration method to be used as an official control method in the framework of Council Directive 70/524/EEC for probiotic bifidobacteria used as feed additives was validated. Seventeen laboratories in 11 European Countries carried out a collaborative study. A spread plate method following BS ISO 15214:1998 using four different agars, Man Rogosa Sharpe (MRS), acidified MRS, MRS with triphenyl tetrazolium chloride (TTC) and a selective bifidobacteria medium, was validated. Precision data in terms of repeatability (r) and reproducibility (R) of the method for each medium using different feeding stuffs with a high and a low inoculation level were determined. Bifidobacteria were present in the samples as a single component or in mixtures with other probiotics. The enumeration of bifidobacteria on all agars showed a relative standard deviation of repeatability (RSD(r)) between 1.2% and 6.3% and a relative standard deviation of reproducibility (RSD(R)) between 2.6% and 8.7%. MRS agar was preferred, followed by acidified MRS and MRS+TTC agar. The selective bifidobacteria medium gave similar counts as the MRS media. For routine analysis, the use of MRS agar with supplementation of cysteine hydrochloride (the selective bifidobacteria medium without antibiotics) is recommended. Depending on the presence and concentration of other probiotics such as enterococci, lactobacilli and pediococci, acidified MRS or MRS+TTC agar is recommended. The selective bifidobacteria medium was selective for bifidobacteria. An official control method for enumeration of probiotic bifidobacteria as a single component and in mixtures with other probiotic microorganisms in feeding stuffs was validated. The methodology is not applicable to mineral feed. The results are intended for consideration for adaptation as CEN and ISO standards.

Animal Feed↗

PubMed2001

Quantitative reverse transcriptase polymerase chain reaction assay for mouse androgen receptor mRNA.

A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay for mouse androgen receptor (AR) mRNA was developed to study relative changes in AR gene expression. Serial dilutions of a standard comprising a fragment of the ampicillin resistance gene flanked by the primer sequences of the AR mRNA were added to a constant amount of total RNA for RT-PCR. Primers were designed to generate a 541-bp fragment of mouse AR mRNA (target [T]) and a 460-bp fragment of the standard (S). PCR products were resolved by gel electrophoresis and quantitated by densitometry. A standard curve was generated for each sample by plotting the logarithm of T/S products vs the logarithm of the amount of S added. The amount of T was determined from the standard curve where intensities of PCR products of T and S were equal. The assay was validated by measuring the relative abundance of AR mRNA in 10 mouse tissues, and results were consistent with studies of AR expression in rat tissues. Assay reproducibility, tested by repeating assays on four different tissues on different days from the RT step, had a coefficient of variation of 6-16%. The current assay is thus both reproducible and valid in quantitation of mouse AR mRNA.

Adrenal Glands↗

PubMed1983

Rapid high pressure liquid chromatographic determination of amitriptyline hydrochloride in tablets and injectables: collaborative study.

A previously reported high pressure liquid chromatographic method for the determination of amitriptyline hydrochloride in dosage forms was modified to permit its use as a stability-indicating method. The modified method, entailing a nitrile bonded microparticulate column, a methanol-0.005M ammonium acetate (90 + 10) mobile phase, and photometric detection at 239 nm, was collaboratively tested by 10 laboratories. Each collaborator received samples of synthetic and commercial tablets and injections. The recovery from a synthetic injection at the 10.06 mg/mL spiking level averaged 98.6%. The amount of declared found in commercial injections averaged 103.1%. The pooled reproducibility SD (CV%) and repeatability SD (CV%) were +/- 2.12 (2.15) and +/- 1.81 (1.84), respectively. The recovery from synthetic tablet composite at the 7.45% spiking level averaged 102.0%. The amount of declared found for commercial 25 mg and 100 mg tablets averaged 96.7 and 97.9%, respectively. The pooled reproducibility SD (CV%) and repeatability SD (CV%) for these 3 tablet samples were +/- 1.89 (1.86) and +/- 1.66 (1.64), respectively. Content uniformity analysis of commercial 25 mg and 100 mg tablets (n = 10) gave amounts of declared values averaging 100.5% (range 92.4-108.8%) and 99.3% (range 89.6-107.0%), respectively. The pooled reproducibility SD (CV%) and repeatability SD (CV%) were +/- 3.23 (3.2) and +/- 2.78 (2.8), respectively. A commercial injectable preparation spiked with dibenzosuberone was also collaboratively analyzed by a thin layer method. The method was adopted interim official first action.

Amitriptyline↗

PubMed1989

[Assay of serum C-reactive protein. Comparison of 3 immunologic methods].

C-reactive protein is a parameter measured in ordinary laboratory routine and is frequently needed rapidly. The authors hereby compare three methods for the measurement of this protein using three common laboratory apparatus: TDX Abbott, BNA Behring and ICS Beckman. The experimental protocol used has been the one defined by the SFBC "Valtec" Commission. Regarding repeatability, the variation coefficients (CV%) are less than 10, except for a CRP value of 16 mg/l on TDX (19.3) and for a value of 56.4 mg/l on ICS (12.5). Reproducibility values confirm repeatability results in the case of TDX, while for ICS CV% are always less than 10. For values between 0 and 133 mg/l the authors have excellent linearity for the three apparatus tested (r = 0.99). The apparatus when compared two by two on 104 patient samples give linear allometric values and correlation coefficients are with acceptable limits (greater than 0.98). It must be noted that there is a difference between results obtained for patient samples and control sera when tested by the different apparatus. ICS necessitates daily calibration and gives the best values with control sera. With BNA the authors obtained more precise values and while TDX remains the easiest to handle, it gives unacceptable imprecise values for low CRP concentrations.

C-Reactive Protein↗

PubMed1988

Diagnostic notes--lumbar BMC reproducibility as evaluated by means of dual photon absorptiometry.

Three evaluations of lumbar bone mineral content (BMC) were carried out at different times at intervals of a few days in 10 normal volunteers aged between 18 and 60. The dual photon absorptiometry technique was employed (using gadolinium-153 as radioactive isotope). Data on 20 subjects aged from 23 to 62 were recorded on magnetic tape and processed ten times by the same operator. The data for individual subjects proved satisfactorily reproducible and the repeated processing of a single scan by the same investigator gave very satisfactory results. The findings demonstrate that the evaluation of lumbar BMC by dual photon absorptiometry can provide highly reproducible and acceptably accurate data.

Adult↗