Gas chromatographic determination of polychlorinated biphenyls (as Aroclor 1254) in serum: collaborative study.

A gas chromatographic-electron capture detection method for determining the concentration of polychlorinated biphenyls (PCBs) as Aroclor 1254 (AR 1254) in serum was evaluated through a 2-phase collaborative study. In Phase I, each collaborator's lot of Woelm silica gel (70-150 mesh) was evaluated for elution and recovery of AR 1254, which had been added in vitro at 25 ng/mL to a serum extract. In Phase II, each collaborator analyzed a series of bovine serum samples that contained the following: (1) in vitro-spiked AR 1254; (2) in vivo AR 1254 and 8 in vitro-spiked chlorinated hydrocarbons; (3) in vivo AR 1254 only; (4) 8 in vitro-spiked chlorinated hydrocarbons only; and (5) neither AR 1254 nor chlorinated hydrocarbons above the detection limit of the method.

Standardization of lipid and lipoprotein determinations for pediatric screening procedures.

Standardization of lipid and lipoprotein measurements is of concern to laboratories that serve pediatric as well as adult populations, since preventive measures taken during pediatric years can help control atherosclerotic cardiovascular problems that can arise during adult years. Multiple analytical and physiologic problems that exist inherently in the lipids and lipoproteins and in application of measurements to the pediatric population must be controlled to gain standardization and produce highly precise and accurate results. Reference values from well-described, observed pediatric populations have been published for use in interpreting analytical results.

International Federation of Clinical Chemistry (IFCC). Scientific Committee, Analytical Section. IFCC/WHO principles and recommendations on evaluation of diagnostic reagent sets used in health laboratories with limited resources. Part 3. Selection and evaluation using reference materials. General considerations.

The purpose of this document is to provide general considerations for the selection and evaluation of clinical chemistry kits in laboratories with limited resources. Separate documents have been developed to provide guidance on experimental procedure, the statistical treatment and interpretation of the data and criteria for acceptable performance of diagnostic kits designed to measure specific analytes.

Determination of steroid hormones in a human-serum reference material by isotope dilution--mass spectrometry: a candidate definitive method for cortisol.

We report a method, based on isotope dilution--mass spectrometry, for determining cortisol in a pooled specimen of human serum. Isotopically labeled cortisol is added to 5.0 mL of serum so that the molar concentrations of labeled cortisol and unlabeled cortisol are approximately equal.

Development of a reference material for alkaline phosphatase.

In developing a Reference Material for alkaline phosphatase, we studied the stability, kinetic properties, and commutability of separate preparations of the purified enzyme from human liver, intestine, bone, and placenta. The Michaelis constants (Km) for the preparations from liver, bone, and intestine agreed well with the Km values we obtained for five human serum specimens, whereas that for the placental isoenzyme differed significantly. The first three isoenzymes exhibited nearly identical response-surface patterns, which closely paralleled those observed for 12 human serum specimens (commutability), but not that of the placental isoenzyme.

Design and demonstration of a quality assurance program for labor-intensive analytical systems.

An interlaboratory quality assurance program was designed and implemented for the analysis of serum for polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs). The two primary means of quality control were analysis of known and blind quality control samples and analysis of blind duplicate serum samples.

Evaluation of potential analytical approach for determination of polychlorinated biphenyls in serum: interlaboratory study.

Forty-four laboratories participated in evaluation of a method for determining polychlorinated biphenyls (PCBs) as AR 1254 in serum at the parts per billion level. The method involves deproteinating serum with methanol, extracting with hexane-ethyl ether, and eluting PCBs from deactivated silica gel for gas-liquid chromatographic determination with electron capture detection. Compounds are quantitated by using the Webb-McCall factors.

Chronological trend in blood lead levels between 1976 and 1980.

Analysis of a chronological trend in data from the second National Health and Nutrition Examination Survey indicated that average blood lead levels in the United States dropped approximately 37 per cent (5.4 micrograms per deciliter) from February 1976 through February 1980. There was no evidence that this trend was due to errors in laboratory measurement or to the design of the survey.

Assessment of methods to determine PCB levels in blood serum: interlaboratory study.

Twenty-five laboratories participated in a study to determine the levels of polychlorinated biphenyls (PCBs) in 3 bovine serum pools, referred to as trial environmental pools (TEPs). TEPs 2 and 3 contained, respectively, low (9.97 ppb) and high (49.

Gas-liquid chromatographic determination of polychlorinated biphenyls and a selected number of chlorinated hydrocarbons in serum.

A method is proposed for concurrently determining the levels of multiple intact exogenous compounds in serum, particularly polychlorinated biphenyls (PCBs) as Aroclor (AR) 1254 and chlorinated hydrocarbons (CHs). Bovine serum pools containing in vivo-bound PCBs (as AR 1254) and in vitro-spiked CHs are used to evaluate the method, which encompasses serum denaturation with methanol, mixed solvent extraction, multiple solvent fractionation from activated silica gel, and determination by electron capture gas-liquid chromatography. Mean recoveries of the in vitro-spiked 9 CHs at levels of 2.

Interlaboratory comparison of serum thyroxine analyses.

Approximately 300 clinical chemistry laboratories participated in a survey of measurements of the thyroxine (T4) concentration in 13 lyophilized serum specimens prepared by spiking a base serum pool with several different levels of T4. Of 35 commercially available kit methods, 4 kits were used by 30 or more laboratories, and 9 by 10 or more laboratories. Values obtained with the Abbott or Nuclear Medical laboratories, kits, which were used by one-third of all laboratories that named a specific kit, averaged 1 to 2 micrograms/dL greater than those obtained with the other methods.

A candidate reference method for uric acid in serum. II. Interlaboratory testing.

We describe the interlaboratory testing of a candidate Reference Method (Part I) for uric acid in serum. The method is based on the ultrasound spectrophotometric quantitation of uric acid before and after incubation with uricase. A comprehensive investigation involving 12 laboratories was organized to document the transferability, intra- and interlaboratory precision, and general reliability of the candidate Reference Method.

A candidate reference method for uric acid in serum. I. Optimization and evaluation.

We describe our optimization and evaluation of a candidate Reference Method for uric acid in serum. Reaction parameters were optimized for a manual, enzymic method for uric acid in which highly purified microbial uricase is used to quantitate uric acid by a differential ultraviolet procedure. We evaluated the method in terms of freedom from interferences, analytical recovery, precision, and comparison with five other uric acid methods.

A candidate reference method for determination of total protein in serum. II. Test for transferability.

The transferability of the candidate Reference Method for total serum protein was tested in eight laboratories in the United States and Europe. National Bureau of Standards SRM 927 (bovine serum albumin) was used in each analytical run as the calibration standard. The mean absorptivity value obtained for this material was 0.

A candidate reference method for determination of total protein in serum. I. Development and validation.

We developed a candidate Reference Method for measuring total serum protein by use of the biuret reaction. The method involves a previously described biuret reagent (Clin. Chem.

Characterization and intermethod relationships of materials containing purified human pancreatic and salivary amylase.

We describe the preparation and characterization of materials containing human pancreatic and salivary alpha-amylase (EC 3.2.1.

A coupled-enzyme equilibrium method for measuring urea in serum: optimization and evaluation of the AACC study group on urea candidate reference method.

We describe a coupled-enzyme equilibrium method for measuring urea in serum, which is performed on supernates prepared by treating each specimen with Ba(OH)2 and ZnSO4 (Somogyi reagent). Analytical recovery of [14C]urea added to a variety of matrices was essentially complete (mean, 100.6%) for the supernates after precipitation.

An interlaboratory study of the determination of digoxin by immunoassay.

We conducted a voluntary survey of laboratories and manufacturers to assess the current quality of analytical assays for serum digoxin. More than 300 clinical laboratories and 18 manufacturers responded, giving data on methods, instruments, computational procedures, and results for five survey samples. We sorted the analytical data to provide statistical information on the grand mean values separately for manufacturers and clinical laboratories, the frequency distribution of all reported values, and the mean values by method of interpolation and algorithms used for linear transformation.

Interlaboratory comparison for results of analyses for polybrominated biphenyls in human serum.

Four hundred and sixty-six "blind" duplicate serum samples were analyzed for polybrominated biphenyls (PBB) by gas chromatography in two laboratories. As calculated by the regression model of Deming, the correlation coefficient for these 466 samples, whose values ranged from nondetectable amount to 1240 parts per billion was 0.9983.