Coefficient Of Variation For Precision Research Articles

Computer-Assisted Technique to Delineate Osteolytic Lesions Around the Femoral Component in Total Hip Arthroplasty

There are currently no ideal quantitative measures assessing osteolysis after total joint arthroplasty. This study reports a new approach for quantification of osteolytic lesions on radiographs of total hip arthroplasty with the hypothesis that computer-assisted lesion quantification improves analysis precision over currently used qualitative visual assessment and thus improves progression monitoring. Duplicate exposure sets of anterior-posterior and frog-leg view radiographs of 15 volunteer total hip arthroplasty patients with radiographically evident periprosthetic lucencies were used. Two independent readers delineated the lesions using on-screen digital marker tools. Based on duplicate readings of the first exposure set only, intraoperator precision had a coefficient of variation (CV) from 1.5% to 3.4%, whereas interoperator precision CV ranged from 3.2% to 4.6%. The reproducibility of the x-ray technique as assessed by single readings of both sets of x-rays was CV 3.2% to 4.8%. The new technique compares favorably to precision of qualitative visual assessment and permits more accurate detection and quantitation of osteolytic lesions.

Microanalysis of amoxicillin, flucloxacillin, and rifampicin in neonatal plasma

Simple and rapid reversed-phase high-performance liquid chromatographic assays with ultraviolet detection have been developed and validated for the determination of amoxicillin, flucloxacillin and rifampicin in neonatal plasma. Plasma samples were either precipitated with perchloric acid (amoxicillin) or methanol (rifampicin) or extracted with methylene chloride (flucloxacillin). Precision coefficients of variation and inaccuracy were less than 15% for all three assays. Only small sample volumes (20-40 microL) were required, making the assays suitable for therapeutic drug monitoring and pharmacokinetic studies in preterm and term neonates. The assays have successfully been applied to analysis of amoxicillin, flucloxacillin and rifampicin in previously published pharmacokinetic studies in neonates.

Quantitative determination of haloperidol in tablets by high performance thin‐layer chromatography

A densitometric high performance thin-layer chromatography (HPTLC) method was developed and validated for the quantitative analysis of haloperidol in tablets. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone/chloroform/n-butanol/acetic acid glacial/water (5:10:10:2.5:2.5 v/v/v/v/v) as the mobile phase. Quantitative analysis was carried out at a wavelength of 254 nm. The method was linear in the 10-100 ng/microL range, with a determination coefficient of 0.999. The coefficients of variation for precision were not higher than 2.35%. The detection limit was 0.89 ng/microL, and the quantification limit was 2.71 ng/microL. The accuracy ranged from 97.76 to 100.33%, with a CV not higher than 4.50%. This method was successfully applied to quantify haloperidol in real pharmaceutical samples, including the comparison with HPLC measurements. The method was fast, specific, with a good precision and accuracy for the quantitative determination of haloperidol in tablets.

Determination of Ceftriaxone in Cerebrospinal Fluid by Ion-Pair Liquid Chromatography

An ion-pair liquid chromatographic assay was developed and validated for the determination of ceftriaxone in cerebrospinal fluid. Chromatographic separation was achieved on a C18 column (125 x 4 mm, 5 microm) with detection at 270 nm, a 1 mL/min flow rate and a 50 microL loop. The mobile phase consisted of 300 mL acetonitrile, 50 mL 0.1M phosphate buffer (pH 7.4), 3.2 g tetrabutylammonium bromide as the ion-pairing agent, and dilution with distilled deionized water to 1 L. Cephradine was used as the internal standard. The assay was linear for ceftriaxone concentrations of 0.5-50 microg/mL. The coefficients of variation for precision were <4.61%. The accuracy ranged from 96.07 to 102.42%. The detection and quantitation limits were 0.019 and 0.065 microg/mL, respectively. This method was used to quantify ceftriaxone in the cerebrospinal fluid of children with meningitis. The results showed that the method described here is useful for the determination of ceftriaxone in cerebrospinal fluid.

Multicentre performance evaluation of the E170 Module for MODULAR ANALYTICS

The E170 module was evaluated at 13 sites in an international multicentre study. The objective of the study was to assess the analytical performance of 49 analytes, and to collect feedback on the system's reliability and practicability. The typical, within-run coefficients of variation (CVs) for most of the quantitative assays ranged between 1 and 2% while a range of 2-4% was achieved with the infectious disease methods. Total precision CVs were found to be within the manufacturer's expected performance ranges, demonstrating good concordance of the system's measuring channels and a high reproducibility during the 2-4-week trial period. The functional sensitivity of 11 selected assays met the clinical requirements (e.g., thyreotroponin (TSH) 0.008 mU/l, troponin T 0.02 microg/l, total prostate-specific antigen (PSA) 0.03 microg/l). The E170 showed no drift during an 8-hour period and no relevant reagent carryover. Accuracy was confirmed by ring trial experiments and method comparisons vs. Elecsys 2010. The reliability and practicability of the system's hardware and software met with, or even exceeded, the evaluator's requirements. Workflow studies showed that E170 can cover the combined workload of various routine analysers in a variety of laboratory environment. Throughput and sample processing time requirements were achieved while personnel 'hands-on-time' could be reduced.

Determination of concentrations of flecainide in human serum by high-performance liquid chromatography on a fluorocarbon-bonded silica gel column

An optimized method for the determination of flecainide in serum is presented. Extraction using a solid-phase C 18 column and chromatography on a stabilized fluorocarbon-bonded silica gel column effectively separate flecainide from an internal standard (a positional isomer of flecainide). The HPLC apparatus and conditions were as follows: analytical column, Fluofix 120N; sample solvent, 20 μl; column temperature, 40°C; detector, Shimadzu RF-5000 fluorescence spectrophotometer (excitation wavelength=300 nm, emission wavelength=370 nm); mobile phase, 0.06% phosphoric acid containing 0.1% tetra- n-butyl ammonium bromide–acetonitrile (75:25, v/v); flow-rate, 1.0 ml/min. The standard curves for flecainide were linear in the concentration range examined (10–2000 ng/ml). The regression equation was y=0.08+0.0078 x ( r=0.9998). The minimum detectable amount of flecainide was approximately 5 ng/ml. In the within-day study, the precision coefficients of variation were 2.66, 2.18, 2.54, 2.72, 2.88, 2.24, and 3.29% for the 10, 50, 100, 200, 500, 1000, and 1500 ng/ml standards, respectively. The absolute recovery rates of flecainide at each concentrations were 94–100%. The method described provides analytical sensitivity, specificity and reproducibility suitable for both biomedical research and therapeutic drug monitoring.

Progress Report of an External Quality Assessment Scheme for Cyclosporine Assay

Beginning in 1987, an external quality assessment (EQA) scheme for cyclosporine (CsA) assay was organized by our Institute and supported by National Research Council (CNR); in 1991, the CNR EQA joined the French CsA interlaboratory program organized by Service de Radiopharmacie et Radioanalyse, University of Lyon. During the last 2 years (1993 and 1994 cycles), > 170 laboratories (from seven European countries) participated in this survey, assaying 44 control samples prepared from pooled blood of heart- and renal-transplant patients; normal pools added with known amounts of CsA were also distributed. During the whole EQA period, a trend toward the use of specific and nonisotopic techniques has been observed. In 1994, 91% of the collected results have been produced by specific methods [high-pressure liquid chromatography (HPLC) or specific immunoassays developed to assay the native molecule of CsA without its metabolites];in the same cycle, the fully automated techniques [TDx, fluorescence polarization immunoassay (FPIA), and enzyme-multiplied immunoassay (EMIT)] accounted for 73% of total results. CsA concentration measured by monoclonal specific immunoassays [(TDx FPIA, radioimmunoassay (RIA) Cyclo-Trac, and EMIT] was well correlated with those from HPLC (r = 0.99-1.00); results from EMIT were very close to those from HPLC, whereas results from RIA Cyclo-Trac and TDx were slightly overestimated (10-20%). Nonspecific methods (TDx polyclonal and nonspecific RIA Cyclo-Trac) measured CsA concentrations 3-4 times higher than those found by HPLC. The cross-reactivity of CsA metabolites in specific immunoassays was estimated from data of patients' samples and spiked samples; an interference of 6% in RIA Cyclo-Trac, 7% in EMIT, and 26% in TDx FPIA was found. The precision coefficient of variation (CV% between laboratory and between assay) of the methods observed in the 1994 EQA cycle was 9.5 for TDx polyclonal FPIA, 10.4 for TDx monoclonal FPIA, 10.5 for EMIT, 10.6 for RIA specific Cyclo-Trac, 14.2 for RIA nonspecific Cyclo-Trac, and 15.2 for HPLC.

Analysis of Periprosthetic Tissue Formation Around a Porous Titanium Endoprosthesis using CT-Based Spatial Reconstruction

Reformatted CT-based image data may be of use in evaluation of new bone formation around massive bone replacement implants, but the impact of metal-induced artifacts on the accuracy of image reconstruction is unknown. This study was designed to evaluate the accuracy and precision of quantitative image reconstruction in the presence of a titanium implant. Model porous-coated titanium implants were harvested from 23 dogs 12 weeks after surgical implantation. Contiguous 1.5 mm transverse CT scans were done first with the titanium implant in place, then repeated after replacement of the implant with an acrylic spacer. Microradiographs of sections cut at defined locations were used to establish gray level thresholds for image reconstruction and to validate the accuracy of CT-based image data. Reformatted image data were used to determine periprosthetic bone volume (mm3) and area of interfacial contact between bone and implant (mm2). The CT-based data derived with either implant material had an accuracy of 83-88% and a precision coefficient of variation (CV) of 2-4% for both volume and contact area variables. Presence of titanium did not seriously affect the quality of images obtained, and results were strongly correlated with those obtained with acrylic. Accurate volumetric data derived from CT-based images of periprosthetic new bone formation can be obtained in the presence of a titanium endoprosthesis. Improved demonstration of spatial relationships of bone and implant may improve postoperative evaluation.

A high-performance liquid chromatographic method for the simultaneous determination of venlafaxine and O-desmethylvenlafaxine in biological fluids.

A rapid, accurate, and sensitive high-performance liquid chromatographic (HPLC) method for simultaneous determination of venlafaxine (V) and O-desmethylvenlafaxine (ODV) in plasma and urine has been developed. V and ODV are extracted from plasma using a liquid-liquid extraction procedure, chromatographed on a Supelcosil LC-8DB column, and quantitated by UV detection at 229 nm. Linearity was established over the range 10-500 ng/ml for V and 7.2-720 ng/ml for ODV using 1.0 ml of human, rat, dog, and mouse plasma. For urine, for both analytes, an analytical range 0.1-10.0 micrograms/ml was established. Accuracy of > +/- 10% about the theoretical mean was achieved for all matrices, with intra- and interday coefficients of variation for precision of < 10%. Endogenous components in plasma and/or urine or known metabolites of V do not interfere in the determination of the analytes. For both V and ODV a quantitation limit of 10 ng/ml for plasma was adequate for their estimation over a period of three half-lives, following administration of a pharmacologic dose in man, and the limit of 0.1 microgram/ml, for urine, can monitor excretion of as little as 0.5% of the dose.

A Rate Nephelometric Phenobarbital and Phenytoin

A new single-point calibration immunoprecipitation inhibition rate nephelometric assay for phenobarbital (PB) and phenytoin (PT) has been evaluated on the Beckman ICS-II analyzer. Within-run precision (n = 20) coefficients of variation (CV) were less than 4.0% for PB (10-44 micrograms/ml) and less than 5.7% for PT (12-34 micrograms/ml). Between-run precision CVs of pooled sera (n = 20) assay were less than 4.2% for PB (7.5-33.8 micrograms/ml) and less than 8.7% for PT (4.5-17.8 micrograms/ml). Linearity and recoveries were good over a broad range of drug levels for both assays. Excellent correlation was found with existing PB, ICS vs. EMIT on the IL Multistat III MCA (y = 1.26 + 1.00x; r = 0.994), ICS vs. Dupont aca (y = 0.832 + 1.01x; r = 0.997), and ICS vs. GLC (y = 0.08 + 0.99x; r = 0.998) methods, and PT, ICS vs. MCA (y = -1.76 + 1.04x; r = 0.985), ICS vs. aca (y = -2.02 + 1.054x; r = 0.987), and ICS vs. GLC (y = -0.26 + 0.990x; r = 0.999) methods. These assays were found to provide accurate drug analyses, good stat or batching capability, and good correlation with existing methods.