Hyperkalemia and pyloric stenosis

Children presenting with pyloric stenosis have hypochloremic metabolic alkalosis and their serum potassium levels are thought to be low or normal. We reviewed potassium levels in infants with pyloric stenosis. Thirty-six percent of patients with pyloric stenosis had increased serum potassium levels. We conclude that hyperkalemia may be more common in children with pyloric stenosis than previously thought.

IMPLICATIONS

A significant number of infants with pyloric stenosis have a serum potassium value above the normal limit.

Bedside glucose testing. Applications in the home and hospital

Point-of-care testing is an increasingly popular means of delivering diagnostic testing closer to the site of patient care. Although point-of-care glucose testing devices have been around for over a decade, concerns about the quality of the results still plague the industry. Changes in federal and state laws that treat point-of-care testing as an extension of the core laboratory promise to improve the quality of testing. The most challenging aspect of quality testing is selection of the appropriate method (core laboratory versus point-of-care test) for the optimal patient outcome.

Development of a universal connectivity and data management system

Point-of-care testing (POCT) is an increasingly popular method of delivering laboratory testing. Management of POCT is challenging given the variety of devices, locations, and staff that need to be coordinated to ensure quality results and meet regulatory guidelines. Electronic capture and transfer of data are preferred for managing POCT, but there is currently no standard method of connecting different devices. Johns Hopkins Medical Institutions (JHMI) developed a common data management system with interfaces to all of its POCT devices. All POCT data are collected in one database and analyzed in a similar fashion. Where data were once collected by carrying laptops to each nursing unit, the POCT devices can now connect directly to the database over the Internet. Algorithms have been created to automate the data analysis and review process. Over the several years that this software has been used, JHMI has experienced improved quality, accuracy, and management of its POCT program. The labor saved by increased automation of data review is refocused on enhancing the performance and scope of the program. Current connectivity and analysis algorithms have future application to remote consultation, management of home self-monitoring patients, and examination of real-time data.

Multiple site analytical evaluation of a portable blood gas/electrolyte analyzer for point of care testing

OBJECTIVE

To evaluate the analytical performance of the SenDx 100 portable blood gas and electrolyte analyzer (SenDx Medical, Carlsbad, CA).

DESIGN

Accuracy was evaluated by correlation of whole blood patient samples with the Nova Stat Profile 5 (Nova Biomedical, Waltham, MA) and the Ciba Corning 865 (Chiron Diagnostics, Medford, MA). Precision was evaluated using quality control materials (RNA Medical, Acton, MA).

SETTING

Critical care laboratories and operating rooms in two institutions.

MEASUREMENTS AND MAIN RESULTS

Precision studies performed at three different concentration levels for each analyte demonstrated intra-assay precision of < or =2.5% coefficient of variation and interassay precision of < or =4.0% coefficient of variation in all cases. Analysis of patient specimens in general showed good to excellent correlation to reference analyzers. Regression variables are tabulated.

CONCLUSIONS

The SenDx 100 portable blood gas and electrolyte analyzer is a simple and easy to use analyzer demonstrating acceptable performance compared with reference methods.

Clinical outcomes of point-of-care testing in the interventional radiology and invasive cardiology setting

BACKGROUND

Point-of-care testing (POCT) can provide rapid test results, but its impact on patient care is not well documented. We investigated the ability of POCT to decrease inpatient and outpatient waiting times for cardiovascular procedures.

METHODS

We prospectively studied, over a 7-month period, 216 patients requiring diagnostic laboratory testing for coagulation (prothrombin time/activated partial thromboplastin time) and/or renal function (urea nitrogen, creatinine, sodium, and potassium) before elective invasive cardiac and radiologic procedures. Overall patient management and workflow were examined in the initial phase. In phase 2, we implemented POCT but utilized central laboratory results for patient management. In phase 3, therapeutic decisions were based on POCT results. The final phase, phase 4, sought to optimize workflow around the availability of POCT. Patient wait and timing of phlebotomy, availability of laboratory results, and therapeutic action were monitored. Split sampling allowed comparability of POCT and central laboratory results throughout the study.

RESULTS

In phase 1, 44% of central laboratory results were not available before the scheduled time for procedure (n = 135). Mean waiting times (arrival to procedure) were 188 +/- 54 min for patients who needed renal testing (phase 2; n = 14) and 171 +/- 76 min for those needing coagulation testing (n = 24). For patients needing renal testing, POCT decreased patient wait times (phases 3 and 4 combined, 141 +/- 52 min; n = 18; P = 0.02). For patients needing coagulation testing, wait times improved only when systematic changes were made in workflow (phase 4, 109 +/- 41 min; n = 12; P = 0.01).

CONCLUSIONS

Although POCT has the potential to provide beneficial patient outcomes, merely moving testing from a central laboratory to the medical unit does not guarantee improved outcomes. Systematic changes in patient management may be required.

Quality assurance, practical management, and outcomes of point-of-care testing: laboratory perspectives, Part I

Pathologists and nurses have only recently cooperated in point-of-care testing (POCT), after accreditation organizations recommended that the laboratories take responsibility for managing the quality of patient-care testing conducted at the bedside. Laboratories are charged with ensuring that patient-care tests generate comparable results, regardless of the location or method. Many home testing devices, when used in hospitals, physicians' office laboratories, and mobile nursing practices, have presented technical and operational issues that were not foreseen from home use. These problems arise from a number of factors: the way the devices are used, the patient population, and even differences in sample type. Thus, to be successful, management of POCT in the health-care environment requires interdisciplinary cooperation of clinical nursing staff and laboratory staff. The article identifies problems in POCT, describes some solutions, and examines how well these solutions have worked from a laboratory perspective.

Technical evaluation of five glucose meters with data management capabilities

Technical performance and data management features are prominent criteria in the selection of an appropriate meter for a point-of-care glucose testing program. We evaluated the technical performance of 5 currently available glucose meters with data management capabilities. The performance of all 5 meters was technically equivalent. Linear regression slopes vs the reference method are in the range of 0.94 to 1.02 and indicate correlation more to plasma values than to whole blood values. The percentage of glucose meter results within +/- 15% of the laboratory value was at least 90%; however, the percentage within +/- 10% was 75% to 87% for most meters. Within-day and between-day precision ranged from 2% to 5% coefficient of variation. Evaluation of linearity with glucose-spiked venous specimens demonstrated that the linearity of each meter agreed with the manufacturer's stated range in most cases. Meter glucose values tended to bias negative as the hematocrit increased, an effect that may be more pronounced at higher glucose concentrations. No volume effects were noted between 5 microL and 40 microL. The results suggest that all meters tested will likely satisfy technical performance criteria in a hospital setting and that selection of a system for point-of-care glucose testing will be influenced by the institution's data management requirements.

Clinical evaluation of Toxi.Prep: a semiautomated solid-phase extraction system for screening of drugs in urine

A prototype Toxi.Prep (TP) system that utilizes solid-phase extraction (SPE) has been developed as a method for broad-spectrum drug screening and identification of tetrahydrocannabinol (THC) metabolites in urine. TP can simultaneously extract up to seven specimens while automating the process of sample extraction, washing, and elution onto a chromatogram. TP was compared with the Toxi. Lab A (TL-A) system for extraction of basic drugs only. In a blind study, 33 distinct drugs and metabolites were detected in 55 urines over 13 runs. Of the drug occurrences, 68.8% (141 of 205) were detected on both TP and TL-A. Of the 13 runs, quinidine and quinine, nortriptyline metabolites, and diphenhydramine were noted more frequently on TP than TL-A, whereas nicotine and metabolites, morphine, and methadone metabolites were more frequently noted on TL-A. Twenty specimens were analyzed for THC metabolites. Of the cases positive for THC metabolites, 100% (16 of 16) were positive by both methods. Time and motion studies for all runs proved an overall labor reduction for extraction and spotting by approximately 40%.

Determination of the spermicide nonoxynol-9 in vaginal lavage by high-performance liquid chromatography

A sensitive normal-phase high-performance liquid chromatographic method using a bonded-phase aminosilica column has been developed for the measurement of the spermicide nonoxynol-9 in vaginal lavage fluid. The mean multiple correlation coefficient (r2) for nonoxynol-9 was 0.999 over the calibration range 3.125-50 micrograms/ml for the standards. Quality control samples measured at two different concentration levels gave intra-day precision values (coefficient of variation, C.V.) in the range of 0.61 to 1.63% and the intra-day accuracy values (mean relative error, M.R.E.) in the range of 0.13-0.62%. Inter-day precision and accuracy values from five different calibration standard concentration values ranged from 2.25 to 5.09% C.V. and 4.02 to 7.56% M.R.E. Nonoxynol-9 samples examined for peak area stability at room temperature over a 24-h time period had a M.R.E. of 14.9%. Quality control samples stored at -70 degrees C, and tested after one month by comparison to baseline samples, had a M.R.E. of -10% and 7.53% for the low and high quality control samples, respectively. The method is sensitive and simple, with short runtimes, to enable the processing of numerous samples from a clinical trial.

Laboratory and bedside evaluation of portable glucose meters

A two-phase, laboratory and bedside, evaluation of blood glucose meters was conducted in this study. Four meters, the AccuData Easy (Boehringer-Mannheim, Indianapolis, IN), HemoCue Glucose (HemoCue, Mission Viejo, CA), LifeScan One Touch II (LifeScan, Milpitas, CA), and Miles Encore QA (Miles, Elkhart, IN) systems, were compared to the Nova Stat Profile 5 (Nova, Waltham, MA) as the laboratory reference. Precision, linearity, correlation to the laboratory method, interference from hematocrit, data management, and operator preference were examined. None of the meters were found to satisfy all of the study's evaluation criteria. Therefore, institutions must weigh which criteria are most important to their individual settings. Although the HemoCue Glucose was found to be technically superior, this meter had no data management capabilities. The Encore QA had greater variance and low bias, whereas the AccuData Easy had bias affected by hematocrit and glucose concentration, and the One Touch II had a negative hematocrit bias and limited linear range when compared to the Nova. Only meters meeting both minimal analytical performance and computerization requirements, the One Touch II and AccuData Easy, were selected for further evaluation. At the bedside, the One Touch II demonstrated performance consistent with the lab evaluation, whereas the AccuData Easy showed greater imprecision in the low glucose range and a correlation that varied with sample type: capillary, venous, or arterial blood. This evaluation indicates that the clinician must interpret near-patient glucose results with respect to meter limitations. FDA approval and marketing statistics, alone, are insufficient to judge the performance of the meters in routine institutional use. Independent method validation, under actual operating conditions, is a better means of predicting future performance of the meters.

Automated HPLC assay of fluoxetine and norfluoxetine in serum

This automated assay determines the concentration of the antidepressant fluoxetine (Prozac) and its active metabolite norfluoxetine in serum by reversed-phase HPLC with spectrophotometric detection. Extraction, injection, and quantification are performed by the Gilson Aspec automated sample handler. The patient's specimen, with added protriptyline as internal standard, is extracted with solid-phase and liquid-liquid methods. Separation is conducted isocratically on a 5-microns (particle size) Supelcosil LC-8-DB reversed-phase column with a triethylamine acetate:acetonitrile mobile phase. The detection limit is 10 micrograms/L and absorbance varies linearly with concentration between 20 and 1,000 micrograms/L for both compounds. Mean recovery was 62% for fluoxetine and 70% for norfluoxetine over linear limits. Within-run and day-to-day imprecision (CV), evaluated at three concentrations (50, 200, and 500 micrograms/L), ranged from 2% to 7%. An extensive interference study of 108 drugs was conducted. Results (n = 58) by the automated method (y) correlated well with those by a manual HPLC method (x): y = 0.96x + 10.20 (r = 0.951, Sylx = 42.9) for fluoxetine, and y = 0.95x - 1.37 (r = 0.917, Sylx = 47.2) for norfluoxetine.

Automated HPLC assay of fluoxetine and norfluoxetine in serum

This automated assay determines the concentration of the antidepressant fluoxetine (Prozac) and its active metabolite norfluoxetine in serum by reversed-phase HPLC with spectrophotometric detection. Extraction, injection, and quantification are performed by the Gilson Aspec automated sample handler. The patient's specimen, with added protriptyline as internal standard, is extracted with solid-phase and liquid-liquid methods. Separation is conducted isocratically on a 5-microns (particle size) Supelcosil LC-8-DB reversed-phase column with a triethylamine acetate:acetonitrile mobile phase. The detection limit is 10 micrograms/L and absorbance varies linearly with concentration between 20 and 1,000 micrograms/L for both compounds. Mean recovery was 62% for fluoxetine and 70% for norfluoxetine over linear limits. Within-run and day-to-day imprecision (CV), evaluated at three concentrations (50, 200, and 500 micrograms/L), ranged from 2% to 7%. An extensive interference study of 108 drugs was conducted. Results (n = 58) by the automated method (y) correlated well with those by a manual HPLC method (x): y = 0.96x + 10.20 (r = 0.951, Sylx = 42.9) for fluoxetine, and y = 0.95x - 1.37 (r = 0.917, Sylx = 47.2) for norfluoxetine.

Isolation of a glycopolypeptide fraction with Lactobacillus bifidus subspecies pennsylvanicus growth-promoting activity from whole human milk casein

Human milk casein samples were digested with trypsin and chymotrypsin, and a glycopolypeptide fraction was isolated from the soluble portion of the digests by a series of gel filtration steps. The glycopeptide fraction stimulated the growth of Lactobacillus bifidus subspecies pennsylvanicius to the same extent as a whey glycopolypeptide fraction previously isolated (Pediat. Res. 10: 1, 1976). It contained between 60 and 70% carbohydrate consisting of galactose, galactosamine, glucosamine, fucose, and sialic acid. This, along with its apparent molecular weight of near 30,000 was also similar to the respective parameters of the whey glycopolypeptide. It is proposed that human milk casein may serve a dual function: that serving the nutritional needs of the breast-fed infant, and that stimulating the growth of L. bifidus subspecies pennsylvanicus. Additionally, the whey glycopolypeptide may arise from casein through proteolysis by an endogenous milk protease.

Glycoproteins from mature human milk whey

Two milk-specific glycoprotein fractions and serum orosomucoid were isolated from mature human milk. One of the milk-specific glycoproteins was homogeneous and was termed glycoprotein A. Its sedimentation and diffusion constants were 2.6 S and 6.3 F, respectively, giving a molecular weight of 29,5000. It contained some 70% carbohydrate consisting of sialic acid, galactose, fucose, glucosamine, and galactosamine. It was not immunologically related to serum orosomucoid. The other glycoprotein, called glycoprotein B, was heterogeneous with an average molecular weight of near 4,000, and carbohydrate comprised some 75% of its weight. Both glycoprotein fractions supported the growth of Lactobacillus bifidus var. Penn. Removal of sialic acid enhanced the growth-promoting activity of glycoprotein B but not of A.

Isolation and characterization of several glycoproteins from human colostrum whey

Five homogeneous closely related glycoproteins were isolated from human colostrum whey, and their molecular weights and carbohydrate contents ranged from 26 000 to 35 000 and from 50 to 80%, respectively. All had the Lactobacillus bifidus var. Pennsylvanicus growth-promoting activity, which was not substantially altered by desialization. Neither human colostrum, milk or the glycoproteins had any cellular immunity-mediating activity. Degradation of the carbohydrate moieties of these glycoproteins indicated that each contained non-identical carbohydrate chains.

Isolation and characterization of a glycoprotein from human colostrum

A glycoprotein was isolated from the M-1 acid glycoprotein fraction of human colostrum. It had a molecular weight of 31200 and contained 27% galactose, 21.7% hexosamine, 8.0% fucose and 10.8% sialic acid by weight. The glycoprotein had no absorption maxima in the 240-300nm region, and was virtually free of ABH(O) and M and N blood-group activity. Alkaline borohydride cleavage of the glycoprotein resulted predominantly in the destruction of threonine and galactosamine.