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PubMed1990

Automated evaluation of tryptic digest from recombinant human growth hormone using ultraviolet spectra and numeric peak information.

UV spectra were successfully employed in identifying peptide fragments from a tryptic digest of recombinant-DNA-derived human growth hormone (r-hGH). It was possible to distinguish very similar peptides utilizing a digital comparison of the UV spectra. An automated procedure was developed to generate a calibration library for the tryptic digest of a reference standard. The calibration library was then evaluated for reproducibility and selectivity and found to provide superior performance in correctly identifying ambiguous peaks as compared to the use of a conventional calibration table. Spectral match factors together with numerical information, derived from peak retention time, area and height, were used to arrive at a "peak score" descriptive of the similarity between standard and sample peaks. "Peak scores" could be combined to calculate a "sample score" indicative of overall similarity between an unknown and a standard. The scoring procedure was automated to generate a final report without operator intervention and successfully assigned appropriate scores to similar as well as dissimilar samples, e.g., native and oxidized r-hGH.

Algorithms↗
PubMed2005

Xanthrochromia? By what method? A comparison of visual and spectrophotometric xanthrochromia.

STUDY OBJECTIVE: Most US hospitals use visual inspection for the detection of cerebrospinal fluid xanthrochromia. We compared visual inspection with spectrophotometric xanthrochromia and studied the effect of tube diameter on the sensitivity of visual inspection. METHODS: Blinded, experienced laboratory technicians visually examined unmarked samples to determine the presence or absence of xanthrochromia. Samples were prepared by lysing RBCs in distilled water. Serial dilutions were placed in clear polystyrene tubes obtained from standard lumbar puncture trays. Laboratory technicians were asked to examine each sample for xanthrochromia using visual inspection. Next, they were asked to interpret the same set of samples with the assistance of a threshold standard. Last, they were asked to interpret the same dilutions, but this time presented in a larger-diameter tube. The absorbance of each sample was measured in a double-beam spectrophotometer at wavelengths between 300 and 700 nm. Samples were said to demonstrate spectrophotometric xanthrochromia if they had an absorbance greater than 0.023 at 415 nm. RESULTS: Sixteen laboratory technicians were shown a total of 160 samples, of which 64 (40%) demonstrated spectrophotometric xanthrochromia. Visual inspection of the samples was 26.6% sensitive (95% confidence interval [CI] 16% to 38%) and 97.9% specific (95% CI 95% to 100%) for spectrophotometric xanthrochromia. Using a reference standard did not improve the performance of visual inspection, but increasing collection-tube diameter increased the sensitivity to 55% (95% CI 43% to 68%). CONCLUSION: Visual inspection is not sensitive for the detection of spectrophotometric xanthrochromia. Increasing the diameter of the collection tubes did improve sensitivity. Emergency physicians should be aware of how xanthrochromia is determined at their institutions and understand the implications of using visual detection to determine the presence or absence of xanthrochromia.

Cerebrospinal Fluid↗
PubMed2001

Ethnic differences in electrocardiographic intervals and axes.

The presence of ethnic differences in electrocardiographic (ECG) patterns is debated. We retrospectively examined the first 1,000 medical files of a multi-ethnic community, where all individuals shared similar living conditions. Only healthy adults (ages 15 to 60 years) were included. All patients had similar socioeconomic, nutritional, environmental, and occupational conditions. Interval and axes measurements were obtained through integrated computerized analysis from a standard 12-lead ECG. ECGs from 597 patients were included in the study: 350 Saudi Arabians, 95 Indians, 39 Jordanians, 17 Sri-Lankans, 39 Filipinos, and 57 Caucasians; 349 patients were men. Interval and axes were compared by analysis of variance. No statistically significant differences were found among ethnic groups in PR interval, QRS duration, QT interval, P wave axis, QRS axis, or T wave axis in men (P =.05). In women, Jordanians had longer QRS duration than Filipinos (87.69 +/- 10.4, 78.81 +/- 5.47 ms, respectively, P =.014). P-wave axis was lower in Filipino women than Saudi, Indian, and Caucasian women (36.87 +/- 26.32, 50.39 +/- 16.88, 52.23 +/- 16.67, 63.19 +/- 14.55 degrees, respectively, P =.002). QRS axis was significantly higher in Filipino than Saudi women (53.06 +/- 26.14, 32.62 +/- 28.31 degrees, respectively, P <.014). There was no ethnic difference in ECG interval measurements in men. However, in women, there were differences in QRS interval, and P and QRS wave axes. Although women had a statistically significant difference in intervals, the magnitude was not clinically significant. Current reference standards for ECG intervals and axes can be used across the ethnic groups studied.

Adult↗
PubMed2003

Human urine certified reference material CZ 6009: creatinine, styrene metabolites (mandelic acid and phenylglyoxylic acid).

The reference material was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to styrene. The concentrations of mandelic acid (MA), phenylglyoxylic acid (PGA), and hippuric acid (HA) in urine were determined by three modes of high-performance liquid chromatography (HPLC). For isochronous stability testing the urinary mandelic acid and phenylglyoxylic acid concentrations were followed over a 24-month period for a preliminary batch by use of HPLC. No changes of the concentration values were found. The creatinine concentration was stable for more than five years. Standard Reference Material NIST 914a Creatinine was used for traceability purposes for creatinine. Pure chemicals MA and PGA were used for traceability purposes. Control material ClinChek-Urine Control (Recipe) was analyzed simultaneously. The mean values of MA and PGA compare well with the means and fall within the control range of control samples. Results from homogeneity, stability, and traceability testing were evaluated using the statistical program ANOVA. The certified values and their uncertainties were evaluated from the results of interlaboratory comparisons, and homogeneity and stability tests. The values are unweighed arithmetical averages of accepted results and their uncertainties are combined uncertainties (coverage factor=1).

Adult↗
PubMed2006

Growth references for Turkish children aged 6 to 18 years.

AIM: To create up-to-date reference standards for Turkish children, and to compare these with growth standards for US children (CDC 2000 Growth Charts) and with previous local data. SUBJECTS AND METHODS: Height and weight measurements of 1100 boys and 1020 girls were obtained by biannual visits to six schools located in relatively well-off districts of Istanbul city. All children came from well-to-do families and all were healthy. All measurements were made by two trained technicians. The LMS method was used in the analyses. RESULTS: Heights of the boys and girls in all age groups were close to the updated 2000 USA growth references and showed an increase from data on Turkish children born 30 y earlier. Weight values were high compared to reference data on US children and to the older data on Turkish children. CONCLUSION: These results indicate that height growth in Turkish school-age children of high socio-economic level conforms to the updated growth data on US children. The data also show a secular upward trend in Turkey. Weight-for-age values indicate an increase in obesity. The results also point to the value of collecting and evaluating local growth data periodically.

Adolescent↗
PubMed1991

A new clinical bioassay for antipyresis.

Three studies that describe antipyretic bioassay are detailed. Reference Standard Endotoxin (RSE) was used to induce fever in healthy male volunteers under randomized, single-dose, double-blind, parallel, and standard drug-control conditions. Thirty minutes before administering RSE, the subjects were medicated with test drug, and oral temperatures were recorded every 15 minutes for 6 to 8 hours. Two NSAIDs and a centrally acting analgesic were evaluated. Both doses of a propionic derivative, three high doses of tebufelone (a new NSAID), as well as the high dose of flupirtine effectively obtunded the fever response to RSE. Adverse reactions consisting of flu-like symptoms such as myalgia, headache, and chills were also significantly reduced with the standard as well as test drugs. The authors conclude that the RSE model is a quick, safe, and reliable method to evaluate antipyresis and to predict other pharmacologic effects of these types of drugs, such as analgesia.

Adult↗
PubMed1981

Arterial blood gas standards for healthy young nonsmoking subjects.

Arterial blood gas analysis has become indispensable for precise physiologic assessment of many lung and heart conditions. Previous studies have related the level of arterial oxygenation to age, smoking habits, and the severity of lung or heart dysfunction. However, no study has reported complete normal blood gas values under all conditions most commonly used by cardiopulmonary laboratories to assess patients. Therefore, we assessed blood gas values in 20 nonsmoking volunteers (ten men, ten women) between 20 and 28 years of age who were healthy (negative heart-lung history and normal results on physical examination, chest radiography, and lung function testing). Blood samples were drawn from the radial artery and measured immediately on a blood gas analyzer. The findings were no significant different (P less than 0.05) in blood gas values among rest (supine), rest (sitting), and exercise (supine) conditions within sex groups; significantly lower mean PCO2 for women than for men under all conditions (except for subjects breathing 100% O2), and a higher pH for women in the rest (supine) position than under other conditions; and a lower mean PCO2 and higher pH for both groups breathing 100% O2. This study provides valid normal arterial blood gas reference standards for routine cardiopulmonary function testing.

Adult↗
PubMed1985

A methodology for evaluating size at birth.

Data from the Swedish Medical Birth Registration, 1977-78, were utilized to develop methods of calculating reference standards for evaluating size at birth. Using the clinical information available, a 'healthy' sub-group was extracted. The individual distributions of birthweight (BW), birth length (BL) and birth headcircumference (BHc) at each week of gestational age (GA) were modelled following some truncation of their ranges. Application of the Box-Cox power family of transformations was generally found to improve the normality of the data. Certain percentages (such as 2.28, 50 and 97.72) were linked through a smoothing device. Features of the results include a positively skewed BW distribution in most GA weeks, a normal positively skewed BW distribution in most GA weeks, a normal distribution of BL and BHc at term, a larger relative variation in BW at lower GA than at term, and a distinct sigmoid shape of the median and other BW curves. Compared with five commonly quoted standards, the present data show the least deceleration in the fullterm region. Disregarding the clinical information, 'primary' sub-groups were also extracted using decomposing techniques. These gave rise to similar BW/GA relationships. Using data from the WHO comparative study, the method just mentioned was applied to standardize BW and BW-specific early neonatal mortality rates. This resulted in an improved description of biological events.

Birth Weight↗
PubMed2006

A comparative study between transmission electron microscopy and immunofluorescence mapping in the diagnosis of epidermolysis bullosa.

The classification of epidermolysis bullosa (EB) into 3 main subtypes has been based on transmission electron microscopy (TEM) that is able to directly visualize and quantify specific ultrastructural features. Immunofluorescence antigenic mapping (IFM) is a technique that determines the precise level of skin cleavage by determining binding sites for a series of antibodies. To date, no study has compared the accuracy of these two techniques in diagnosing the major types of EB. A prospective cohort of 33 patients thought to have EB on clinical grounds had TEM, IFM, and genetic testing performed. The sensitivities and specificities of TEM and IFM were calculated compared with the genetic results. Of 33 cases, 30 had a positive EB diagnosis. TEM subclassified EB into its three major forms in 24/30 cases (80%) and IFM in 29/30 cases (97%). Overall, TEM sensitivities and specificities when compared with genetic results were 71% and 81%, respectively. IFM sensitivities and specificities when compared with genetic results were 97% and 100%, respectively. If a patient tested positive for EB by IFM, the likelihood ratio of having a particular type of EB was consistently greater than 20 against the reference standard (compared with a likelihood ratio less than 10 for TEM). Our results indicate that the diagnosis of EB is improved (sometimes substantially) by the use of IFM compared with TEM.

Adolescent↗
PubMed1994

Evolution of methods for assessing ciguatera toxins in fish.

Ciguatera toxins are odorless, tasteless, and generally undetectable by any simple chemical test; therefore, bioassays have traditionally been used to monitor suspect fish. Many native tests for toxicity in fish have been examined, including the discoloration of silver coins or copper wire or the repulsion of flies and ants, but all of these were rejected as invalid. Oral feeding of fish to cats or mongoose is a simple and relatively sensitive assay, but cats often regurgitate part of the meal. Feeding tests described above have been used in screening fish for toxicity, but they are cumbersome and nonquantitative. A mouse bioassay was developed; unfortunately, this procedure requires purification fish extracts, since mice are not very sensitive to ciguatoxin. An alternative to the use of mice is the mosquito bioassay, which was recently used to obtain a dose-response relationship between ingested ciguatoxin and clinical symptoms in man. This assay correlates reasonably well with cat and mouse bioassay. Many other bioassays have been developed using chicken, brine shrimp, and the guinea pig atrium. All traditional bioassays have one common disadvantage, the lack of specificity for individual toxins. Recent studies have also focused on the development of chemical methods, i.e., TLC and HPLC, for the detection and quantification of ciguatera-related toxins (okadaic acid and ciguatoxin and its analogs). Alternative assays based on immunochemical technology have been developed and show the greatest promise for use in seafood safety monitoring programs. For earlier methods (RIA and ELISA formats), liver extracts from ciguatoxic eels were used to prepare ciguatoxin antisera. The assay has been further adapted to a solid-phase immunobead assay (S-PIA), which has a very high potential for use as a marketplace screening tool to separate ciguateric fish. This assay can also be used to monitor reefs for ciguatera potential. Historically, attempts to validate methods used to measure ciguatera toxicity have been plagued with a lack of specificity and reference standards. These restrictions have been resolved, and a study is under way to evaluate the precision and accuracy of a low-cost, simplified field and laboratory S-PIA kit (Ciguatect, Hawaii Chemtect International, Pasadena, California, 91109), through an international interlaboratory trial using the AOAC/IUPAC validation mechanism.

Animals↗
PubMed2001

A novel extrinsic reference method for assessing the vitamin A value of plant foods.

BACKGROUND: The amounts of vitamin A that are metabolically derived from specific carotene-containing foods are largely unknown. OBJECTIVE: We sought to develop an improved method for estimating the metabolic vitamin A potential of provitamin A carotenoids by using [2H4]retinyl acetate (d4-RA) as an extrinsic reference standard. DESIGN: Healthy subjects consumed a standardized test meal containing 6 mg beta-carotene as either raw carrot or spinach, either 20 or 1 g added fat, and 6.0 micromol d4-RA. Concentrations of unlabeled (d0) retinyl esters (RE), labeled (d4) RE, and carotenoids in the plasma triacylglycerol-rich lipoprotein fraction (d < 1.006 kg/L) were determined in serial blood samples with HPLC and gas chromatography-mass spectrometry. Baseline-corrected areas under the curve for d0-RE, d4-RE, and carotenoids were calculated, and the masses of absorbed d0-retinol and carotenes were estimated assuming 80% absorption of the d4-RA reference dose. RESULTS: In trials with ample (20 g) fat (n = 6), 7 +/- 4% of the 6 mg beta-carotene ingested was taken up as beta-carotene plus RE with 0.3 +/- 0.1 mg as retinol. Test meals without carotenes yielded no beta-carotene or d0-RE response and there was no effect of treatment (either fat amount or vegetable, n = 6) on the mean d4-RE area under the curve. The lower-than-expected vitamin A yields were attributed to poor intestinal uptake rather than to low conversion of beta-carotene to RE. CONCLUSION: The triacylglycerol-rich lipoprotein and d4-RA method, which controls for variation in chylomicron kinetics in vivo and RE recovery during analysis, is useful for obtaining quantitative estimates of the vitamin A potential of single meals.

Adult↗
PubMed1984

Picogram per cell determination of DNA by flow cytofluorometry.

Using nuclei isolated from less than 0.2 g tissue or 10(7) cells, a method is presented for the quantitative determination of amounts of DNA per cell at the picogram level. This technique is based on the enhanced fluorescence of 4',6-diamidino-2-phenylindole (DAPI) when it binds to DNA. A rapid, one-step nuclear isolation and DNA staining procedure is used to prepare tissue samples for flow cytometric analysis. Frozen tissues give results comparable to those for fresh tissue. Both chicken and trout erythrocyte nuclei were used as reference standards in the determination of amounts of DNA per diploid cell for several mammals and Amazon molly fish. The consistent values obtained for different tissues from the same organism show the accuracy of this method for DNA measurement.

Animals↗
PubMed1992

Blood pressure measurements in the nursing home: are they accurate?

To examine the accuracy of blood pressure (BP) measurements in the nursing home, a trained observer (physician) and nursing home staff (NHS) measured BP for 146 nursing home residents on two separate occasions. Using the physician as the reference standard for measuring BP, the NHS: 1) significantly underestimated systolic BP; 2) significantly overestimated diastolic BP; and 3) had a high frequency of terminal digit preference for zero. These errors resulted in the NHS misclassifying hypertension in 21% of patients.

Aged↗
PubMed2000

Identification and characterization of Podophyllum emodi by API-LC/MS/MS.

An API-LC/MS/MS method was developed for the identification of the medicinal herb Podophyllum emodi based on the profile of its aryltetrahydronapthalene and related lignan marker compounds. This was done by matching the structural information from the tandem mass spectrometric data with those lignan marker compounds already reported for the herb. The method could be employed in the absence of reference standards for the markers and was particularly useful in view of the scarcity of supply of these chemical standards. It has been used successfully to differentiate Podophyllum emodi from two commonly used medicinal herbs of a different genus but having similar appearance, Radix clematidis and Radix gentiana, as well as a closely related herb, Podophyllum peltatum.

Biomarkers↗
PubMed2006

Accuracy of pelvic flexion measurements from lateral radiographs.

Variations in pelvic orientation affect preoperative planning decisions, intraoperative navigation, and postoperative measurements. By providing the means to measure pelvic flexion at low cost and reporting pelvic flexion using the standard reference system, a lateral radiograph technique based on the pubic tubercles and anterior superior iliac spines may be useful for studying functional pelvic orientation and functional alignment and for improving accuracy of postoperative measurement. We evaluated the accuracy of this method by synthesizing 50 lateral pelvic radiographs. Six observers performed manual landmark-based pelvic flexion measurements on the resultant radiographs. Pelvic flexion measurement errors were small (0.004 masculine +/- 1.38 masculine). Apart from one outlier with an error of 12.4 masculine, the errors ranged from -4.0 masculine to 3.0 masculine. The data suggest that accurate measurements of pelvic flexion can be made from lateral radiographs with respect to the standard anatomic reference system. However, failure to correctly observe a landmark can introduce large errors. Therefore, the clarity of the relevant landmarks should be considered carefully before applying this technique. Lateral radiographs can be easily acquired and analyzed, making this technique convenient and inexpensive.

Body Weights and Measures↗
PubMed2006

Quantitative multiplexed C-reactive protein mass spectrometric immunoassay.

Reported in this work is the development and application of a high sensitivity mass spectrometric immunoassay for the quantitative analysis of C-reactive protein from human plasma. Multiplexed affinity retrieval devices and methodology were developed to simultaneously target retinol binding protein, C-reactive protein, serum amyloid P component, as well as an added exogenous internal reference standard (staphylococcal enterotoxin B) for subsequent MALDI-TOF MS analysis. This approach allows for semiquantitative analysis of both retinol binding protein and serum amyloid P component while performing absolute quantitative measurements of C-reactive protein. The ability to qualitatively differentiate between all three human proteins and their associated variants is also maintained. Standard curve, QC, and human plasma samples were analyzed in a high throughput manner, which performed with a CV < 15%. The resultant human plasma sample C-reactive protein quantitative measurements were then compared to those achieved with a high sensitivity latex immunoturbidimetric assay.

C-Reactive Protein↗
PubMed1986

Detection of rotavirus with a new polyclonal antibody enzyme immunoassay (Rotazyme II) and a commercial latex agglutination test (Rotalex): comparison with a monoclonal antibody enzyme immunoassay.

A total of 176 human fecal specimens were examined for the presence of rotavirus by four different assays: a monoclonal antibody enzyme immunoassay; the original polyclonal antibody enzyme immunoassay marketed by Abbott Laboratories, North Chicago, Ill. (Rotazyme I); a modification of this assay which is now commercially available (Rotazyme II); and a latex agglutination test (Rotalex) recently introduced by Medical Technology Corp., Somerset, N.J. In addition, selected specimens were examined for the presence of rotavirus by electron microscopy, immune electron microscopy, and RNA gel electrophoresis. A total of 40 specimens were positive in the monoclonal antibody enzyme immunoassay, and 136 were negative. Using the results obtained with this procedure as the reference standard, we found the sensitivities of the Rotazyme I, Rotazyme II, and Rotalex tests to be 97.4, 100, and 81.6%, respectively. The specificities of these three procedures were 88.8, 83.9, and 100%, respectively.

Antibodies, Monoclonal↗
PubMed2001

The cross-sectional area of supraspinatus as measured by diagnostic ultrasound.

We have established a reference standard for the cross-sectional area (CSA) of supraspinatus as measured by diagnostic ultrasound. The influence of hand dominance and of ageing on the CSA was also assessed. We examined 72 subjects aged from 20 to 79 years. Standard values of the CSA were determined with a high measure of interobserver reliability. Although the CSA on the dominant side was significantly larger (p < 0.001) by 0.16 cm2 (95% CI 0.072 to 0.249) than that on the non-dominant side, this difference had no clinical significance. The CSA of supraspinatus decreased significantly with ageing.

Adult↗