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PubMedDate not supplied

Petrifilm rapid S. aureus Count Plate method for rapid enumeration of Staphylococcus aureus in selected foods: collaborative study.

A rehydratable dry-film plating method for Staphylococcus aureus in foods, the 3M Petrifilm Rapid S. aureus Count Plate method, was compared with AOAC Official Method 975.55 (Staphylococcus aureus in Foods). Nine foods-instant nonfat dried milk, dry seasoned vegetable coating, frozen hash browns, frozen cooked chicken patty, frozen ground raw pork, shredded cheddar cheese, fresh green beans, pasta filled with beef and cheese, and egg custard-were analyzed for S. aureus by 13 collaborating laboratories. For each food tested, the collaborators received 8 blind test samples consisting of a control sample and 3 levels of inoculated test sample, each in duplicate. The mean log counts for the methods were comparable for pasta filled with beef and cheese; frozen hash browns; cooked chicken patty; egg custard; frozen ground raw pork; and instant nonfat dried milk. The repeatability and reproducibility variances of the Petrifilm Rapid S. aureus Count Plate method were similar to those of the standard method.

Colony Count, Microbial↗

PubMed2001

Interlaboratory comparison of dynamic olfactometry in Central Europe 2000.

This paper presents the results of an interlaboratory comparison (ringtest) on olfactometry with 31 participants from four countries in Central Europe. The aim was to give evidence of the performance of dynamic olfactometry on the basis of the European Standard prEN 13725 (Draft) "Determination of odour concentration with dynamic olfactometry. The test included the analysis of three individual substances (n-butanol, hydrogen sulphide, tetrahydrothiophen) as well as a natural odour mixture (coffee flavour) to compare mean values and the standard deviations of results for the investigated samples. It was confirmed that laboratories working in compliance with the requirements of the new standard achieve a significantly better repeatability and reproducibility than those that are not compliant.

Environmental Monitoring↗

PubMed2001

Determination of arsenic in water--quality assurance and calculation of metrological characteristics.

Arsenic is a toxic element, acting as a nerve poison and proven carcinogen. Its main source for humans is drinking water where the most important are arsenic (V) compounds. With respect to the Slovak standard, in force since 1998, the maximum tolerable value is defined as the important characteristic of drinking water. If the value 0.01 mg.l-1 of arsenic is exceeded, water is not drinkable. The mentioned standard defines criteria for precision of the arsenic determination and the corresponding limit of detection--being 10% of the maximum tolerable value. Arsenic content in the drinking water samples was measured by the AAS method. Internal Quality Control for analysis by the ETA AAS method was based on the harmonised guidelines recommended by IUPAC, ISO and AOAC. The following metrological characteristics were calculated: precision, accuracy, and the yield of the arsenic standard addition to the studied sample--matrix spike and analytical spike. In addition to it, a thorough study of the limit of detection, LOD, and the limit of quantification (determination), LOQ, was performed. The LOD and LOQ values were calculated in the traditional way as well as by the ULA technique, newly recommended by IUPAC. In the latter case, the calculated LOD value was close to the demanded 10% limit of the maximum tolerable value, which is 1 microgram.l-1 As. The repeatability and reproducibility, found at two concentration levels 56.02 +/- 0.73 micrograms.l-1 and 6.0 +/- 0.9 microgramsl-1, were 3.2% and 3.9%, respectively, and 7.1% and 9.8%, respectively. Trueness of the applied AAS method was proven satisfactory on the reference material SRM 1643 Trace Elements in Water.

Arsenic↗

PubMedDate not supplied

Dry rehydratable film method for rapid enumeration of coliforms in foods (3M Petrifilm Rapid Coliform Count plate): collaborative study.

A rehydratable dry-film plating method for coliforms in foods, the 3M Petrifilm Rapid Coliform Count plate method, was compared with the U.S. Food and Drug Administration's Bacteriological Analytical Manual method for nondairy foods and the American Public Health Association's Standard Methods for the Examination of Dairy Products (SMEDP) method for dairy foods. Six food types, vanilla ice cream, cheddar cheese, fresh refrigerated uncooked pasta, wheat flour, prepared frozen macaroni and cheese, and frozen hash browns, were analyzed for coliforms by 11 collaborating laboratories. For each food product tested, the collaborators received 8 blind samples consisting of a control sample and 3 levels of inoculated sample, each in duplicate. The mean log counts for the methods were comparable. The repeatability and reproducibility variances of the Petrifilm Rapid Coliform Count method at 14 and 24 h were not significantly different from those of the standard methods.

Cheese↗

PubMed1975

Use of a lyophilized reference plasma to compare coagulation test procedures: Normotest, Simplastin-A and Thrombotest.

In 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy. Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers' procedures used to set "normal percentage activity", as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents. The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents. The assigned coagulation activity of batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

Anticoagulants↗

PubMedDate not supplied

Validation of real-time PCR analyses for line-specific quantitation of genetically modified maize and soybean using new reference molecules.

Novel analytical methods based on real-time quantitative polymerase chain reactions by use of new reference molecules were validated in interlaboratory studies for the quantitation of genetically modified (GM) maize and soy. More than 13 laboratories from Japan, Korea, and the United States participated in the studies. The interlaboratory studies included 2 separate stages: (1) measurement tests of coefficient values, the ratio of recombinant DNA (r-DNA) sequence, and endogenous DNA sequence in the seeds of GM maize and GM soy; and (2) blind tests with 6 pairs of maize and soy samples, including different levels of GM maize or GM soy. Test results showed that the methods are applicable to the specific quantitation of the 5 lines of GM maize and one line of GM soy. After statistical treatment to remove outliers, the repeatability and reproducibility of these methods at a level of 5.0% were <13.7 and 15.9%, respectively. The quantitation limits of the methods were 0.50% for Bt11, T25, and MON810, and 0.10% for GA21, Event176, and Roundup Ready soy. The results of blind tests showed that the numerical information obtained from these methods will contribute to practical analyses for labeling systems of GM crops.

DNA, Plant↗

PubMed2002

Stability of a NDIR analyser for CO2 at atmospheric concentration.

Carbon dioxide monitoring is significant in the environmental field since this gas plays an important role in the greenhouse effect. In order to determine CO2 concentration and to develop simulation models, it is necessary to carry out measurements which are accurate and comparable in time and space, i.e. SI-traceable. Non-dispersive infrared (NDIR) analysers are employed for CO2 measurements, as they are precise and stable. In order to achieve traceability, such instruments have to be characterized and calibrated. At the Istituto di Metrologia "G. Colonnetti"--CNR, a procedure for calibrating NDIR analysers for CO2 at atmospheric level was developed, which enables to calculate a correction for the analyser output. In addition, a complete uncertainty analysis was carried out and a correct traceability chain was established. The goal of the present work is the study of the stability of a NDIR analyser by repeating calibrations during three years and comparing the correction curves obtained to identify a proper re-calibration interval for such analysers. The investigated instrument has good repeatability and reproducibility, hence satisfactory stability during time, as shown by the short-term and long-term compatibility of calibration curves.

Atmosphere↗

PubMedDate not supplied

Determination of nitrogen solubility in dilute pepsin hydrochloric acid solution of fishmeal: interlaboratory study.

A revised method to determine solubility of nitrogen in dilute pepsin, using 0.0002% pepsin in place of 0.2% in AOAC Official Method 971.09, was tested in 16 laboratories with 12 samples of fishmeal. Results were calculated according to 2 procedures: AOAC Official Method 971.09 and a method described in 1964 by researchers at the Torry Research Station (Aberdeen, Scotland), and generally referred to as the modified Torry method. Variations in the method of shaking and source of pepsin were also investigated. Pepsin solubility values were lower and more variable when calculated by the Torry procedure. The method of shaking apparently affected the result when calculated according to the Torry but not the AOAC method. The source of pepsin had no significant effect on between-laboratory variability, but a comparison of the 2 main sources within one laboratory resulted in highly significant differences. Based on this study, the International Fishmeal and Fish Oil Organization has adopted this new method, using 0.0002% pepsin but keeping the AOAC method of calculation. The type of shaker and source of pepsin are recommended but are not mandatory. The repeatability and reproducibility limits of this new method are 1.6 and 3.3% units of solubility, respectively.

Algorithms↗

PubMed1976

[Frequency of amebiasis and other intestinal protozoal diseases. An epidemiological study with the aid of MIF technic].

Advantages and disadvantages of various laboratory techniques used for the diagnosis of intestinal protozoa are discussed. The importance of a correct parasitological diagnosis is emphasized. The MIF procedure has been investigated with regard to its reliability and found to be very effective due to its high diagnostic yield and reproducibility in repeated examinations. The incidence rates found in our material agreed well with those in the literature, thus enhancing the value of the MIF procedure. The feces of 1005 persons returning from the tropics during the first 8 months of 1975 have been examined by the MIF technique and assessed for intestinal protozoa. Apathogenic amebae were found four times as often as E. histolytica. The incidence was 52.7/1000 for E. histolytica and 70.6/1000 for Giardia lamblia. Multiple parasitosis is often diagnosed. E. histolytica is very likely to be encountered when two or three apathogenic amebae are present.

Eukaryota↗

PubMed2003

Experimental verification of conditions for near infrared spectroscopy (NIRS).

OBJECTIVES: in vitro assessment of the reproducibility and the optimal separation and position of the optodes in continuous wave (CW-) NIRS measurement of local inhomogeneities in absorption and/or scattering. METHODS: a CW- NIRS system (OXYMON) was used with laser diodes at wavelengths of 767 nm, 845 nm, 905 nm, 945 nm and 975 nm. For practical considerations (dimensions of neonatal head) the measurements were performed on a cylindrical tissue-equivalent phantom (70 mm diameter of base material with mua = 0.01 mm(-1) (800 nm) and mu's = 1.00 mm(-1) (800 nm)), containing rods with 10 x absorption, or 10 x scattering, and 5 x both Monte Carlo simulations were carried out of a cylinder with transport scattering coefficient mu's = 0.525 mm(-1) and absorption coefficient mua = 0.075 mm(-1) and two optode positions. RESULTS: reproducibility of repeated measurements (n = 10) was +/- 0.005 OD. Maximum OD in case of absorbing rod, and of absorbing + scattering rod was measured with optodes separated by 90 degrees and rod position angle symmetrically (45 degrees ) in between. Minimum OD for these rods was obtained with optodes at 150 degrees angle and rod position at 240 degrees (i.e. relative to transmitting optode position at 0 degrees ). A second maximum OD was obtained at an optode angle 180 degrees and rod position at 180 degrees. Maximum OD (i.e. attenuation) for the scattering rod was at optode separation angle of 90 degrees and rod at 0 degrees. Minimum OD for this case was obtained with optode angle of 180 degrees and rod positions around 80 degrees and 280 degrees. Maximum OD changes by absorbing rod were in the order of +0.12 OD and -0.04 OD, respectively. Simulations at an optode separation angle of 90 degrees showed a spatial sensitivity path enclosing the rod position at maximum absorption found experimentally. CONCLUSIONS: when considering the phantom as a realistic geometrical model for the neonatal head, it can be concluded that the optode position at 90 degrees angle would be optimal for detecting an inhomogeneity at 15 mm depth, i.e. the location of the periventricular white matter. Since the rods are relatively strongly different from the base material the question remains to be answered whether local ischemia, which might lead to irreversible brain damage, can be detected by CW-NIRS

Computer Simulation↗

PubMed1976

Pancreatic, gallbladder, and gastric responses to intraduodenal calcium perfusion in man.

To determine the effect of intraduodenal calcium on pancreatic, gallbladder, and gastric functions in healthy man, a validated perfusion method was employed to quantify total pancreatic, biliary, and gastric outputs during duodenal perfusion of either 6 mM, 12 mM,or 25 mM of elemental calcium (as isotonic calcium chloride solutions). Intraluminal calcium stimulated pancreatic enzyme secretion and gallbladder contraction in a dose-related fashion, achieving comparable responses to those produced by intravenous cholecystokinin-pancreozymin (CCK-z). Responses to calcium were reproducible when repeated in the same individual. Gastric acid outputs and serum gastrin levels increased significantly only with higher calcium perfusions (25 mM). Although duodenal calcium perfusion (25 mM) slightly increased serum calcium concentrations, induced hypercalcemia (by intravenous calcium infusion) of similar magnitude had no effect on pancreatic or gallbladder function. It is suggested that intraduodenal calcium may induce release of CCK-PZ (and/or other neurohormonal factors) from the gut, causing stimulation of these digestive organs.

Adult↗

PubMed2002

Serological methods for potency testing of tetanus toxoid vaccines for human use.

A collaborative study has been performed to validate two in vitro serological assays, ELISA and ToBI test, as alternatives to the direct challenge procedure for potency testing of tetanus toxoid vaccines for human use (Ph.Eur. monograph Tetanus vaccine (adsorbed) (0452)). In six laboratories, guinea-pigs were immunised with tetanus toxoid vaccines from different manufacturers representing various types of combined products, including one product of borderline quality. Blood samples were taken two to four days before challenge. Parameters that were analysed included: (i) correlation of vaccine potencies obtained by direct challenge test and by serological assays, (ii) prediction of survival based on antibody concentrations, and (iii) correlation of antibody concentrations obtained in ELISA, ToBI test and in vivo Toxin Neutralisation test. In addition, ELISA and ToBI test repeatability and reproducibility were further studied by titration of a total of 28 serum samples in 23 laboratories. This paper provides background information, gives an outline of the experimental design and discusses the study results. It is concluded that ELISA and ToBI test are valid alternatives to the challenge procedure. Implementation of the serological assays as alternatives to the challenge procedure for batch release of tetanus vaccines for human use will result in a marked refinement as well as a substantial reduction of numbers of laboratory animals.

Animals↗

PubMed1976

Further methodological studies on the intravenous fat tolerance with Intralipid emulsion.

Factors affecting the reproducibility of the intravenous fat tolerance test (IVFTT) with the Intralipid emulsion have been studied in man. Temperature variations of the emulsion at the time of injection did not affect the fractional removal rate k2. Plasma samples could be treated at room temperature without affecting the k2 value. Linear k2 slopes were obtained also in pronounced hypertriglyceridaemia, which suggests that the test can be applied in subjects with wide ranges of serum triglyceride (TG) concentrations. In subjects with a wide range of serum lipids but at steady state with regard to lipid metabolism, the IVFTT was found to be highly reproducible when repeated with intervals of up to 6 months. Furthermore, the turnover of serum TG, determined as the product of the fractional removal rate and the serum TG concentration, was constant. Most Intralipid batches gave identical k2 results. In some comparisons, batches were found which gave k2 curves significantly different from the standard batches. It is recommended that the IVFTT is carried out only with Intralipid emulsions that have been standardized in this respect.

Cholesterol↗

PubMed2002

Quality control and quality assessment of coagulation tests in Japan.

We have used prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (Fbg), and fibronogen/fibrin degradation products (FDP) as screening coagulation tests, and antithrombin III (AT III), plasminogen (Plg), alpha2-plasmin inhibitor (alpha2-PI), protein C (PC), thrombin-AT III complex (TAT), plasmin-alpha2-PI complex (PIC), and D-dimer as special coagulation tests. We report the present condition of internal and external quality control for these coagulation tests in Japan. We made a summary report of internal quality control of some coagulation tests in Division of Hematology Laboratory, Department of Laboratory Medicine, Hokkaido University Hospital. The repeatability and reproducibility of screening tests were good, but those of special tests were partly adequate. We have participated in some external quality control surveillance including Japan Medical Association (JMA), Japanese Association of Laboratory Medical Technologists (JALMT), College of American Pathologists (CAP), and some commercial quality control surveillance. We also reported the results of some external quality control surveillance.

Blood Coagulation Tests↗

PubMed1992

Construction of a model eye and its applications.

Construction details are given of a model eye, based on the Bennett and Rabbetts schematic eye. It incorporates a cornea, lens, and spherical fundus. Distilled water filled the anterior and vitreous chambers. By means of a micrometer screw, the vitreous chamber depth can be precisely varied to produce axial ametropia from +11 to -17 D. Readings taken over the greater part of this range with a Topcon Autorefractor RM-A6500 were found to be repeatable and reproducible within +/- 0.25 D. The model eye was used to investigate the relationship between the actual size of a fundus feature and its photographic image in two different fundus cameras. With a Zeiss Oberkochen camera of telecentric design the magnification was found to remain constant whatever the degree of axial ametropia, whereas with a Carl Zeiss Jena camera the magnification varied linearly with ametropia. A technique developed by Littmann for determining the actual size of a retinal feature when using a fundus camera of telecentric design is discussed briefly.

Eye↗

PubMed2003

Establishment of European Pharmacopoeia BRP batch 2 for inactivated poliomyelitis vaccine for in vitro D antigen assay.

A collaborative study was initiated by the European Directorate for the Quality of Medicines (EDQM) to assign a potency value for the candidate Ph Eur BRP batch 2 against the 2nd International Standard (IS) in order to replace the dwindling stocks of Ph Eur BRP batch 1. The candidate material is a concentrated trivalent bulk (Type 1 (Mahoney), Type 2 (MEF1) and Type 3 (SAUKETT)) from a commercially available IPV vaccine. Nine laboratories participated in the collaborative study. Eight laboratories reported results. Participants performed in-house ELISA assays on the candidate BRP, the 2nd International Standard (IS) and the current BRP (BRP batch 1). An additional sample was included to acquire information on the correlation between the in vitro and in vivo assays based on comparison with a previous study. Results of that comparison are included as an annex. Potency estimates were satisfactory in terms of repeatability and reproducibility, however the estimates for the 2nd IS were significantly lower than those for Ph Eur BRP batch 1. These two reference standards are derived from the same material and were originally assigned the same potency value after a joint study run by EDQM and the WHO in 1994. A reconciliation study was therefore designed to determine if the IS stored at NIBSC and the IS which had been sent from NIBSC to EDQM for use in the initial study were equivalent. 3 of the laboratories from the initial study participated. Results revealed no significant difference between the 2nd IS stocks stored in the two different locations at NIBSC nor between BRP batch 1 and the standards stored at NIBSC for types 1 and 2. For type 3 the 2nd IS standards stored at NIBSC are 13 % less potent than the Ph Eur BRP batch 1. The 2nd IS which had been shipped from NIBSC to EDQM was significantly less potent than BRP batch 1 and the 2nd ISs stored at NIBSC for all three types, confirming the observation of the initial study. Possible explanations for this apparent loss of potency of the 2nd IS used in the study are under investigation. Since Ph Eur BRP batch 1 and the 2nd IS in stock at NIBSC appear no more different than when their original potency assignment was made at their establishment, and since the 2nd IS standard used in the initial part of this study was compromised, a consensus potency value for the candidate BRP was determined using Ph Eur BRP batch 1 as the reference standard. The candidate material was therefore assigned a potency of 320-67-282 D Antigen units/ml (IU) for types 1, 2 and 3 respectively. A stability monitoring program will be initiated. The candidate material was adopted by the European Pharmacopoeia Commission at its session in March 2003 as European Pharmacopoeia IPV vaccine BRP batch 2 for D Ag in vitro assay.

Animals↗

PubMedDate not supplied

3M Petrifilm Staph Express Count plate method for the enumeration of Staphylococcus aureus in selected types of meat, seafood, and poultry: collaborative study.

The 3M Petrifilm Staph Express Count plate method was compared with AOAC Official Method 975.55 for the enumeration of Staphylococcus aureus in selected foods. Four foods--cooked, diced chicken; cured ham; smoked salmon; and pepperoni--were analyzed for S. aureus by 12 collaborating laboratories. For each food tested, the collaborators received 8 blind test samples consisting of a control sample, a low inoculation level, a medium inoculation level, and a medium inoculation level with background flora, each in duplicate. The mean log10 counts for the methods were comparable for all 4 foods. The repeatability and reproducibility variances of the 24 h Petrifilm Staph Express Count plate method were similar to those of the 72 h standard method.

Animals↗

PubMedDate not supplied

3M Petrifilm Staph Express Count plate method for the enumeration of Staphylococcus aureus in selected types of processed and prepared foods: collaborative study.

The 3M Petrifilm Staph Express Count plate method was compared with AOAC Official Method 975.55 for the enumeration of Staphylococcus aureus in selected foods. Five foods--frozen lasagna, custard, frozen mixed vegetables, frozen hashbrowns, and frozen batter-coated mushrooms--were analyzed for S. aureus by 13 collaborating laboratories. For each food tested, the collaborators received 8 blind test samples consisting of a control sample, a low inoculation level, a medium inoculation level, and a medium inoculation level with background flora, each in duplicate. The mean log10 counts for the methods were comparable for all 5 foods. The repeatability and reproducibility variances of the 24 h Petrifilm Staph Express Count plate method were similar to those of the 72 h standard method.

Agaricales↗