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PubMed2004

A comparison between liking ratings obtained under laboratory and field conditions: the role of choice.

The relationship between laboratory and field data was investigated for nine different groupings of 5-7 foods: two main dish groupings, four snack item groupings, and three specific meals. Liking ratings on the nine-point hedonic scale were obtained in an US Army field study and for the same foods in a sensory laboratory. In a subsequent choice simulation laboratory with two food groupings, we offered subjects some choice (three out of six or seven items) among to which foods they would evaluate. The results showed high correlations between lab and field ratings for the snack food groupings (0.58-0.94), but low correlations for the main dishes (-0.05-0.26) and meal components (-0.07-0.41). Correlations between mean field and mean laboratory data improved when laboratory subjects were offered a choice of foods. The ability of laboratory ratings to predict acceptability of foods consumed under realistic conditions appears to depend on the type of food, and may be better for foods used as snacks than for main dishes. Laboratory conditions in which subjects had some degree of choice among foods improved the relationship with the field data. It is important to pay more attention to experimental variables that may improve the validity of sensory laboratory tests.

Adult↗
PubMed1998

Differences between local investigator and core laboratory interpretation of the admission electrocardiogram in patients with unstable angina pectoris or non-Q-wave myocardial infarction (a Thrombin Inhibition in Myocardial Ischemia [TRIM] substudy).

The present study compares the on-site interpretation of an admission electrocardiogram (ECG) with core laboratory results in a large, multicenter trial of 516 patients diagnosed with unstable angina pectoris or non-Q-wave myocardial infarction. The local investigators evaluated the admission ECG regarding ST-T changes before the ECGs were sent to the core laboratory for blinded interpretation. The strength of agreement between the observations was described by kappa statistics. There was a poor agreement regarding identification of ST-segment elevation, with 17 patients identified by the local investigator versus 92 by the core laboratory (kappa = 0.05). There was a fair agreement on ST-segment depression with 158 patients diagnosed on-site versus 64 by the core laboratory (kappa = 0.38). Identification of T-wave inversion demonstrated good agreement with 306 patients diagnosed on-site versus 280 by the core laboratory (kappa = 0.63). A moderate agreement regarding identification of a normal ECG was found with 101 patients on-site versus 135 in the core laboratory (kappa = 0.42). Independent variables, including peak creatine kinase-MB and 30-day outcome, were more closely related to core laboratory results than the local investigator's interpretation of the admission ECG. Thus, in the present study, considerable differences were demonstrated between the on-site interpretation of the admission ECG and the blinded evaluation performed in the core laboratory regarding relatively simple electrocardiographic variables. The results suggest that more widespread use of independent evaluation of clinical data should be incorporated in future clinical trials.

Aged↗
PubMed1999

Sediment toxicity and stormwater runoff in a contaminated receiving system: consideration of different bioassays in the laboratory and field.

Several field and laboratory assays were employed below an urban storm sewer outfall to define the relationship between stormwater runoff and contaminant effects. Specifically, two bioassays that measure feeding rate as a toxicological endpoint were employed in the field and in the laboratory, along with bioassays measuring survival and growth of test organisms. In 7 to 10 d in situ exposures, amphipod leaf disc processing, growth and survival were monitored. Different exposure scenarios were investigated by varying the mesh size (74 microns or 250 microns mesh) and method of deployment (water column, sediment surface, or containing sediment) of in situ exposure chambers. Hyalella azteca, Daphnia magna, and Pimephales promelas survival were monitored in 48 h in situ exposures. Feeding inhibition was investigated via enzyme inhibition of H. azteca and D. magna and via leaf disc processing measurements of the detritivore H. azteca. Additionally, we investigated the extent of phototoxicity at this site via field exposures in sun and shade and laboratory exposures with and without UV light. The measurement of detritivore leaf disc processing, and thus its usefulness as an endpoint, was hindered by individual variability in the amount of leaf consumed and by leaf weight gain during the summer field exposures. For D. magna, enzyme inhibition measured in a laboratory exposure did not reveal the toxicity observed in field exposures. For H. azteca, enzyme inhibition measured in the laboratory indicated toxicity similar to that observed in short term chronic in situ exposures. Enzyme inhibition also did not detect differences in toxicity due to variations in flow conditions. There were no statistically significant effects of any exposure on P. promelas survival or H. azteca growth, and there were no statistically significant effects due to mesh size or sun exposure. Survival of H. azteca was the most sensitive and the least variable endpoint. Effects on survival were noted in the same treatments over short-term chronic exposures in the laboratory and in situ. Significant differences in survival were noted due to the method of deployment under low flow conditions. In situ chambers containing sediment resulted in greater mortality in the 10 d low flow in situ experiments. Under high flow conditions, significant reductions in survival and leaf disc processing were noted under all methods of deployment at the two impacted sites over a 7 d exposure. Also under high flow conditions, significantly greater mortality of H. azteca was reported at the downstream field site when sediment was included in the chamber at deployment. These results suggest that significant toxicity at this site is due to accumulation of contaminants in the sediment and the mobilization of these contaminants during a storm event. In situ exposures detected toxicity not observed in laboratory exposures. These results suggest that a combination of laboratory and field bioassays is most useful in defining field effects.

Animals↗
PubMed2001

Laboratory diagnosis of central nervous system infections.

The laboratory diagnosis of CNS infection is essential for optimal therapy. Acute infection requires rapid turn-around testing with high predictive values, that is, the ability of a test to accurately identify those patients who do or do not have disease caused by a specific etiology. The Gram's stain, fungal stains of direct smears, antigen testing for C. neoformans, and culture of bacteria, fungi, mycobacteria, and some viruses are important tests for the diagnosis of acute infection. The laboratory diagnosis of chronic infection necessitates discussion between the clinician and laboratory technician to allow triaging of testing. Antigen tests for bacteria, fungi, and viruses; antibody tests for multiple microorganisms; and PCR testing for bacteria, M. tuberculosis, and many viruses are all important in limited clinical situations. All testing for acute or chronic disease depends on sufficient specimen that is transported to the laboratory in a manner that will not compromise viability or chemical integrity. Sterile containers that maintain moisture content, exclude oxygen for anaerobic requests, and are stored at proper temperatures (22 degrees C room, 4 degrees C refrigeration, or -20 degrees C freezer depending on pathogen and test) are mandatory. Many laboratory issues addressing the diagnosis of CNS infection are changing or evolving. Most important is the recognition that bacterial antigen testing for the diagnosis of acute bacterial meningitis rarely impacts patient management and is not routinely needed, CSF shunt infections differ from usual meningeal infections and require rapid diagnosis, and TB meningitis remains a difficult disease to diagnosis but may be confirmed first by PCR testing of CSF. In addition, Whipple's disease of the CNS can be confirmed using PCR with CSF; CJD has a marker protein, referred to as 14-3-3 antigen, that can be detected in CSF, and the diagnosis of fungal CNS disease requires careful interpretation of direct smears, antigen and antibody testing, and culture. Most difficult to diagnose among the CNS infections are viral meningitis and encephalitis. The appearance of new etiologies, such as West Nile virus, and the common use of PCR for the herpes viruses and enteroviruses represent important advances. Evolving methods for the laboratory diagnosis of CNS infection represent significant improvements over previous testing; however, the array of tests available demands more attention for appropriate selection, is significantly more expensive, and requires new skills for performance and interpretation. The responsibility for proper use of laboratory testing lies both with the clinician and laboratory technician.

Antigens, Bacterial↗
PubMed1998

A comparison of laboratory data in perinatal transfers at Baystate Medical Center and transferring hospitals.

Objective: Perinatal transfers come to Baystate Medical Center (BMC), a tertiary hospital with level III nursery, for treatment of pregnancy-related complications such as preterm labor, PPROM, PIH, diabetes, and bleeding problems. We postulated that Baystate Medical Center, a teaching hospital, must repeat most of the laboratory tests ordered by the community hospitals transferring these pregnant patients.Methods: A comparison of laboratory tests ordered by the transferring hospital and Baystate Medical Center was done in a retrospective chart review. Among the 92 charts reviewed, 42 perinatal transfer patients with PTL and PPROM, excluding patients with diabetes, PIH, and other complications, were included in the study.Results: A significant difference (P <.001 by Student t test) was found between the number of laboratory tests ordered by Baystate Medical Center and the outside hospital. Ten laboratory tests, such as white count, hematocrit, differential, cervical cultures, urinalysis and culture, tox screen, type and screen, and ultrasounds, were ordered by BMC in comparison to only three laboratory tests ordered by the transferring doctors. In comparing patients directly admitted to Baystate for PTL or PPROM with the perinatal transfer patients, there was no significant difference between the number of laboratory tests ordered. However, perinatal transfers had a greater percentage of PPROM and delivery prior to 36 weeks.Conclusion: In conclusion, there is limited redundancy in laboratory testing in perinatal transfer patients when they are transferred from one institution to the another. Diagnosis of PTL is difficult and a panel of laboratory tests have become standards in finding causes at BMC. Allowing the tertiary hospital to work up the perinatal transfer patients is an efficient way of allocating health care.

Journal Article↗
PubMed1999

Point-of-care and standard laboratory coagulation testing during cardiovascular surgery: balancing reliability and timeliness.

OBJECTIVE: The use of point-of-care technology has increased faster than efforts to validate its effectiveness compared to standard laboratory testing modalities. To address this issue with a current point-of-care coagulation system (HEMOCHRON Jr, International Technidyne Corporation (ITC), Edison, NJ), we designed a study to test the hypothesis that data obtained from point-of-care coagulation equipment correlates with data obtained from standard laboratory coagulation equipment. One of the potential advantages gained using point-of-care testing is the ability to obtain more rapid results. To address this issue, turnaround time, defined as the elapsed time (in minutes) from when the sample was acquired from the patient until the investigators knew the results, was also determined. METHODS: Following Human Investigation Committee approval and informed consent, a prospective study was conducted to compare results obtained from point-of-care coagulation equipment with those results obtained from standard laboratory coagulation equipment. The study was performed in three groups of patients undergoing cardiovascular surgery, each requiring different levels of anticoagulation. RESULTS: Of the 83 patients who met the inclusion criteria, the correlation (combining data from groups 1-3) between results obtained from point-of-care and standard laboratory prothrombin time was r = 0.867, p < 0.001. The correlation (group 3) between point-of-care and standard laboratory international normalized ratio was r = 0.943, p < 0.001. The correlation (combining data from groups 1 & 2) between point-of-care and standard laboratory activated partial thromboplastin time was r = 0.825, p < 0.001. Median turnaround time for the standard laboratory was 90 minutes, with a mean turnaround time of 74 to 78 minutes, depending upon the group. In contrast, the median turnaround time for point-of-care testing was two minutes and 14 seconds. CONCLUSIONS: The results from this study population reveal that data obtained from point-of-care prothrombin time, international normalized ratio and activated partial thromboplastin time results correlate with results obtained from standard laboratory coagulation testing. The value of obtaining reliable results in a timely fashion offers a potential advantage for point-of-care testing in dinical situations, such as in the operating room, where saving time may translate into financial savings.

Aged↗
PubMed2001

A proficiency testing scheme for aromatic hydrocarbons in air by the manual thermal desorption-GC method: a comparison of laboratory performance with the uncertainty requirements of the European Union Ambient Air Directive.

The Workplace Analysis Scheme for Proficiency (WASP) is a proficiency testing scheme for the analysis of occupational hygiene and environmental air samples and is operated in the UK by the Health and Safety Laboratory. Since 1997, WASP has offered samples of benzene, toluene and m-xylene, at environmental levels on Tenax, and has about 35 laboratories participating, mostly from industry, local government and consultancy organisations in the UK. The results reported cover the first 10 rounds of the environmental analytes (1997-1999) and demonstrate the important role of proficiency testing in assessing the quality of laboratory performance. Estimates are obtained for within-laboratory precision and the total variability at each analyte level. The estimates of within-laboratory precision suggest that laboratories have more difficulty analysing toluene and m-xylene than benzene. Linear relationships for the reproducibility relative standard deviation (RSDT) with loading level are evident for the analytes at occupational levels. At environmental levels, the relationship between loading level and reproducibility is much less well defined. The standard deviation for the proficiency testing assessment for all three analytes at the environmental level is 14%, as derived from the benzene data. Expanded uncertainty estimates (k = 1.96), for the analysis of samples since the scheme started, are obtained from the average total variance, and are 27% for benzene, 39% for toluene and 36% for m-xylene. Although the linear trend of performance against round number was not significant at the 95% level of confidence (p = 0.23 for benzene, p = 0.3 for toluene and p = 0.32 for m-xylene), there was a general improvement in RSDT from 26-34% to about 8-13% 10 rounds later. Currently, for a laboratory to meet one of the data quality objectives in the Ambient Air Directive (indicative measurement of benzene, expanded uncertainty +/- 30% or less), it would have to achieve a level of analytical performance to satisfy the category 1 (best performance) limit of better than +/- 8.8%. In the last proficiency testing round, discussed in this paper, only 58% of laboratories obtained performance scores that indicated that they were able to consistently achieve this level of performance.

Air Pollutants↗
PubMed2002

Relationship between coronary angioplasty laboratory volume and outcomes after hospital discharge.

BACKGROUND: Although an inverse association has been established between short-term complications of percutaneous coronary interventions (PCIs) and the volume of angioplasty procedures performed by catheterization laboratories, no data are available on the association between laboratory volume and long-term outcomes. METHODS: A cohort study of 25,222 patients undergoing PCI in 43 laboratories in Pennsylvania from October 1994 to December 1995 was performed by use of the Pennsylvania Health Care Cost Containment Council database. The association of laboratory volume with inhospital, 1-month, and 6-month events was estimated by use of multivariable analyses adjusting for patient and procedural characteristics. RESULTS: Although a higher volume of procedures was associated with reduced inhospital coronary bypass ([CABG] 0.6 odds ratio [OR] for > or =400 vs <400 PCIs/year; 95% CI 0.4, 0.8), it was not associated with CABG occurring within 1 month after discharge (P =.71; OR 1.0, 95% CI 0.6, 1.7). Laboratory volume was also not significantly associated with postdischarge revascularization (PCI or CABG) at 1 month (P =.58; OR 1.1, 95% CI 0.8, 1.4) or 6 months (P =.47; OR 1.04, 95% CI 0.91, 1.19). In addition, laboratory volume was not associated with rates of myocardial infarction (P =.14), death (P =.28), or the combined outcome of PCI, CABG, myocardial infarction, or death (P =.90) at 1 month after hospital discharge. CONCLUSIONS: Although our study confirmed the volume/complication relationship for inhospital CABG, it did not reveal an association between volume and postdischarge events. These results suggest that inhospital complications will remain the standard for assessing laboratory volume and that selective use of higher-volume laboratories may not improve long-term outcomes.

Aged↗
PubMed1998

Reliability of disc diffusion susceptibility testing of Streptococcus pneumoniae and adjustment of laboratory-specific breakpoints. Finnish Study Group for Antimicrobial Resistance.

A routine disc diffusion method for detecting antibiotic-resistant Streptococcus pneumoniae was evaluated in 20 clinical microbiology laboratories. Fifty consecutive clinical isolates were tested by disc diffusion in each laboratory, and collected for MIC determinations. Participating laboratories used three disc types and several media; altogether 17 disc-medium-breakpoint reference combinations were used. Of the 781 isolates, 1.2% were resistant to penicillin and 4.2% were intermediately resistant. Eight of the nine resistant isolates had been classified as resistant to penicillin using a 1 microgram oxacillin disc screening test in the participating laboratories. If the MIC was taken as 0.125 mg/L, which is just above the intermediate breakpoint, 11 of 12 isolates were interpreted as susceptible to penicillin with the oxacillin disc test. The laboratories using Oxoid or Biodisk paper discs performed better in detecting co-trimoxazole resistance than the laboratories using Rosco tablets. Two control strains (one multiresistant and one susceptible) were each tested in the laboratories ten times. Based on these results laboratory-specific breakpoints for tetracycline were determined linearly. These adjusted breakpoints corrected three of five false-susceptible interpretations of the resistant clinical isolates and reduced the number of minor errors from 8.5% to 2.6%.

Anti-Bacterial Agents↗
PubMed2001

Evaluation of inter-scorer and inter-laboratory reliability of the mouse epididymal sperm aneuploidy (m-ESA) assay.

The mouse epididymal sperm aneuploidy (mESA) assay using 3-chromosome fluorescence in situ hybridization (FISH) was recently developed for assessing the aneugenic potential of chemicals on male germ cells. This study was designed to identify the major technical factors that affect inter-scorer and inter-laboratory variability of the mESA assay. Two laboratories participated in this study (GSF and Lawrence Livermore National Laboratory, LLNL). Mice (102/ElxC3H/El) F(1) were exposed in one laboratory (GSF) to vinblastine (VBL; single intraperitoneal injection of 0, 0.5, 1.0 or 2.0 mg/kg), one of the 10 priority compounds of the Commission of the European Communities (CEC) Aneuploidy Program. Twenty-two days later the mESA assay was applied to analyze sperm aneuploidy. In the initial evaluation, small but statistically significant differences were found between the two laboratories in baseline frequencies and there was also disagreement in the determination of a VBL aneuploid effect. Therefore, experiments were conducted to identify the sources of the inter-laboratory differences and technical factors that affected assay reliability and the VBL study was repeated. A harmonization experiment was conducted by bringing the microscope scorers from both laboratories to the same site (LLNL) for a cross-training exercise. Following this exercise, a second group of VBL-treated and control mice were evaluated, and we concluded that VBL is not a sperm aneugen. Our research has identified scoring criteria as the major source of inter-laboratory variation and emphasizes the importance of strict technical controls for the mESA assay, including controlling slide preparations for treatment-induced reductions in sperm count, coding of slides and selection of statistical tests. These considerations are particularly important for the interpretation of small effects (< or =2-fold) on sperm aneuploidy. Our findings suggest that 2-fold differences in frequencies can result from differences among scorers, samples and treatment groups, and are readily within the normal variation for the mESA assay. Such small differences should be viewed with caution until independently confirmed.

Aneuploidy↗
PubMed1982

A prospective analysis of laboratory tests and imaging studies to detect hepatic lesions.

A prospective study of the ability of laboratory tests and liver imaging tests to detect hepatic metastases was performed. Eighty patients at risk for hepatic metastases but without clinical evidence of disease were tested with 13 laboratory tests and three liver imaging tests. No single laboratory test had greater than 65% accuracy in the detection of hepatic lesions. No combination of the laboratory tests increased this accuracy. If the laboratory tests were used with one of the liver imaging tests, the accuracy was improved in some combinations to 76%. The CEA assay when analyzed in patients with colorectal primaries had an accuracy of 79%. The results show that the laboratory tests alone are not sufficiently accurate to detect liver metastases. Additional accuracy can be obtained by the combined use of a single liver imaging test and selected laboratory tests. Use of all the liver imaging tests and laboratory tests lowers the accuracy and increases the expense and thus is unnecessary.

Carcinoembryonic Antigen↗
PubMed1986

Importance of laboratory parameters in the evaluation of Crohn's disease activity.

Some laboratory investigations are abnormal during the course of Crohn's disease (CD). We investigated the trend of some of these laboratory tests in a group of patients with CD to study the relationships between an activity index made up of such laboratory parameters only (LCDAI) and the usual Crohn's disease activity index (CDAI). One hundred thirty-one examinations of 63 patients were evaluated. At each investigation, besides calculation of the CDAI, 10 laboratory investigations were carried out. Three gastroenterologists independently gave an overall evaluation of the laboratory activity for each of the 131 examinations on the basis of the results of the blood tests alone. The sum of the evaluations was used as an independent variable on which a laboratory index was developed by multiple regression analysis. C reactive protein, red cell sedimentation rate, acid alpha 1-glycoprotein, alpha 1-antitrypsin, and white blood cells had an important share in the development of this laboratory index. The evaluation of the relationships existing between LCDAI and CDAI showed that in patients with moderate to severe clinical disease activity, LCDAI was constantly altered. The same happened in 55% of cases in clinical remission, which suggests an inflammatory activity that is not clinically evident. These results point to the advisability of supplementing a predominantly clinical index, such as CDAI, with a laboratory index such as LCDAI in the evaluation of CD.

Crohn Disease↗
PubMed1988

Comparison of the cardiovascular effects of different laboratory stressors and their relationship with blood pressure variability.

Laboratory stressors are employed to assess the 'typical' cardiovascular reactivity to stress of a given subject. It is believed that this may assist in the diagnosis of hypertension and predict future development of blood pressure (BP) elevation. However, the internal consistency of the data obtained by laboratory stressing manoeuvres and their ability to reflect the effects of everyday stressful events occurring over a 24-h period have never been clearly established. We studied a group of ambulant normotensive and essential hypertensive in-patients who were undergoing prolonged intra-arterial blood pressure monitoring (Oxford method) to determine firstly, whether four routine laboratory stressors provided a homogeneous evaluation of subjects' reactivity and secondly, whether cardiovascular reactivity to these stressors reflected a tendency of BP to vary over a 24-h period. A significant correlation (P less than 0.01) was found between the pressor responses to mental arithmetic and the mirror drawing test and between the pressor responses to the cold pressor test and hand-grip. These correlations, however, were not close and responses to the 'mental' and 'physical' stressors were unrelated. The elevation in BP induced by laboratory stressors also did not correlate with the increase in BP accompanying stress elicited outside laboratory conditions (i.e. doctor's visit). The pressor effects of both the laboratory and the out-of-laboratory stressors showed little or no correlation with the 24-h absolute or per cent blood pressure variabilities, although for the stressors involving a mental challenge, a significant though not close correlation with daytime blood pressure variability was found. These data underline the limitations of laboratory tests in assessing cardiovascular reactivity to stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Relationship of common laboratory parameters to the activity of Crohn's disease in children.

The Pediatric Crohn's Disease Activity Index (PCDAI) has been proposed as a simple instrument to aid in the classification of patients by disease severity. The PCDAI includes subjective patient reporting of symptoms, physical examination, nutritional parameters, and several common laboratory tests (hematocrit, erythrocyte sedimentation rate, albumin). In this report we examine the relationship of each of the laboratory parameters to the PCDAI, as well as to a modified Harvey-Bradshaw Index score and physician global assessment of disease activity. Data were gathered from the clinical and laboratory observations from 133 children and adolescents at 12 pediatric gastroenterology centers in North America. A statistically significant relationship (p less than 0.05) was noted between each of the laboratory tests and the PCDAI for patients with either disease limited to the small bowel or in those with colonic involvement. For patients with disease limited to the small bowel, a statistically significant (p less than 0.05) relationship was also noted between the three laboratory parameters and the modified Harvey-Bradshaw Index and global assessment. For patients with large-bowel involvement, the erythrocyte sedimentation rate was statistically related to the modified Harvey-Bradshaw Index and global assessment (p less than 0.01), as was hematocrit to global assessment (p less than 0.01). Although the laboratory parameters used in the PCDAI appear to generally reflect disease activity in most patients, no single laboratory test is adequate to reflect disease activity in all patients. Future work will need to identify additional laboratory measures to reflect the inflammatory process and serve as important adjuncts in the assessment of disease activity.

Adolescent↗
PubMed1983

Comparative study of Streptococcus mutans laboratory strains and fresh isolates from carious and caries-free tooth surfaces and from subjects with hereditary fructose intolerance.

This study was undertaken to investigate and compare some biochemical and physiological properties related to sugar metabolism of 4 laboratory strains and 13 freshly isolated strains of Streptococcus mutans from carious and caries-free tooth surfaces and from subjects with hereditary fructose intolerance. Growth in Trypticase (BBL Microbiology Systems)-yeast extract in the presence of various sugars was almost the same for all of the fresh isolates, which grew generally better than the laboratory strains. This was especially noticeable on sucrose where the fresh isolates (including those isolated from hereditary-fructose-intolerant patients) grew two to four times more rapidly than the laboratory strains. The rate of acid production by the fresh isolates, measured with resting cells in the presence of glucose, was quite comparable to the rate of the laboratory strains. The glucose analog, 2-deoxyglucose, inhibited the acid production from glucose by two laboratory strains (6715 and ATCC 27352), but none of the fresh isolates was affected by its presence. The antibiotic, gramicidin D, which allows free diffusion of H(+) across the cell membrane, inhibited the acid production of all of the strains. Phosphoenolpyruvate phosphotransferase activity toward alpha-methylglucoside was found in all of the laboratory and freshly isolated strains. 2-Deoxyglucose phosphotransferase activity was detected in all of the laboratory strains, but many clinical strains, especially those from hereditary-fructose-intolerant patients, contained very low or almost undetectable 2-deoxyglucose phosphotransferase activity. In one strain, the activity was restored after repeated culturing in Trypticase-yeast extract medium supplemented with glucose. Glucokinase and lactate dehydrogenase activities were detected in all of the strains tested. No marked differences were observed for these two enzymes between the fresh isolates and the laboratory strains except for three clinical strains which possessed low levels of glucokinase. The growth of all of the strains in a broth containing 4 mM glucose and 4 mM lactose was studied. Various patterns were observed: diauxie, glucose utilized before lactose but without diauxie, both sugars consumed concurrently, and lactose consumed more rapidly than glucose.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1996

Reliability of nucleic acid amplification for detection of Mycobacterium tuberculosis: an international collaborative quality control study among 30 laboratories.

Nucleic acid amplification to detect Mycobacterium tuberculosis in clinical specimens is increasingly used as a laboratory tool for the diagnosis of tuberculosis. However, the specificity and sensitivity of these tests may be questioned, and no standardized reagents for quality control assessment are available. To estimate the performance of amplification tests for routine diagnosis, we initiated an interlaboratory study involving 30 laboratories in 18 countries. We prepared blinded panels of 20 sputum samples containing no, 100, or 1,000 mycobacterial cells. Each laboratory was asked to detect M. tuberculosis by their routine method of nucleic acid amplification. Only five laboratories correctly identified the presence or absence of mycobacterial DNA in all 20 samples. Seven laboratories detected mycobacterial DNA in all positive samples, and 13 laboratories correctly reported the absence of DNA in the negative samples. Lack of specificity was more of a problem than lack of sensitivity. Reliability was not found to be associated with the use of any particular method. Reliable detection of M. tuberculosis in clinical samples by nucleic acid amplification techniques is possible, but many laboratories do not use adequate quality controls. This study underlines the need for good laboratory practice and reference reagents to monitor the performance of the whole assay, including pretreatment of clinical samples.

Bacterial Typing Techniques↗
PubMed2002

Accuracy and precision of the CoaguChek S versus laboratory INRs in a clinic.

BACKGROUND: The CoaguChek S is the next-generation coagulation monitor for measuring the international normalized ratio (INR) that replaces the CoaguChek device. Studies are lacking comparing the CoaguChek S with local laboratory INR assessment to ensure its accuracy and precision for monitoring patients on anticoagulation. OBJECTIVE: To evaluate accuracy, precision, and technical ease-of-use of the CoaguChek S compared with laboratory measurements. METHODS: Accuracy was evaluated in 101 patients by parallel assessment of INRs (CoaguChek S and laboratory); precision was evaluated in 31 patients using duplicate INRs from CoaguChek S and laboratory and from liquid quality controls. Accuracy was determined using orthogonal regression, Bland-Altman plot, and clinical applicability (INRs discrepant in categorization of INR goal and resulting in different therapeutic decisions). Precision was examined by comparing mean difference +/- SD between repeated INRs from CoaguChek S and laboratory, coefficient of variation (CV), and coefficient of repeatability (CR). The influence of low and elevated INRs on accuracy and precision was also examined. To assess ease-of-use of the monitor, the number of technical errors was recorded. RESULTS: The CoaguChek S significantly correlated to laboratory measurement (r = 0.93); 16.7% of INRs resulted in discrepant categorization and 24.5% would have required a different therapeutic plan. The CV and CR compared well between CoaguChek S and laboratory (6% vs. 4.9%; 0.455 vs. 0.346, respectively). When subgroups of INR values <4.0 and <3.0 were evaluated, the precision improved with both methods. Precision, based on liquid quality controls, was good (CV 4.6% = low-level; 3.3% = high-level). The CoaguChek S was found to have an error rate of 1.8%. CONCLUSIONS: The CoaguChek S is an accurate and precise alternative to laboratory assessment of the INR at values <4.0; it is an efficient device with a low likelihood of errors during testing.

Aged↗
PubMed2000

A model for a multicentre approach to the derivation of reference intervals for thyroid hormones and testosterone for laboratories using identical analysers.

Ideally, every laboratory should derive their own reference intervals for all analytes, but this is difficult in practice. A survey, by questionnaire, of UK laboratories using the Chiron Diagnostics ACS:180 (Chiron Diagnostics Limited, Halstead, Essex, UK), for thyroid function tests, showed that 10% of laboratories derived their own reference intervals, 60% quoted values "adapted" from intervals for previous methods, whilst the remaining 40% quoted (often incorrectly) reference intervals supplied by the manufacturer. In addition only 13% of respondent laboratories derived their own reference intervals for testosterone. As a result of this survey, a study was devised to enable the users of the Chiron Diagnostics ACS:180 immunoassay system to develop and use within-method, between-laboratory reference intervals for thyroid hormones and testosterone. Laboratory collaboration provided the recommended minimum number of data points by establishing a reference sample group. This sample group was used for the calculation of appropriate reference intervals for each hormone according to the guidelines published by the IFCC. We propose this approach as a model for laboratories using identical instrumentation to produce, through collaboration, within-method, between laboratory reference intervals.

Female↗