The effects of an educational meeting and subsequent computer reminders on the ordering of laboratory tests by rheumatologists: an interrupted time series analysis

OBJECTIVES

To examine the effects of an educational meeting and subsequent computer reminders on the number of ordered laboratory tests.

METHODS

Using interrupted time series analysis we assessed whether trends in the number of laboratory tests ordered by rheumatologists between September 2012 and September 2015 at the Sint Maartenskliniek (the Netherlands) changed following an educational meeting (September 2013) and the introduction of computer reminders into the Computerised Physician Order Entry System (July 2014). The analyses were done for the set of tests on which both interventions had focussed (intervention tests; complement, cryoglobulins, immunoglobins, myeloma protein) and a set of control tests unrelated to the interventions (alanine transferase, anti-cyclic citrullinated peptide, C-reactive protein, creatine, haemoglobin, leukocytes, mean corpuscular volume, rheumatoid factor and thrombocytes).

RESULTS

At the start of the study, 101 intervention tests and 7660 control tests were ordered per month by the rheumatologists. After the educational meeting, both the level and trend of ordered intervention and control tests did not change significantly. After implementation of the reminders, the level of ordered intervention tests decreased by 85.0 tests (95%-CI -133.3 to -36.8, p<0.01), the level of control tests did not change following the introduction of reminders.

CONCLUSIONS

In summary, an educational meeting alone was not effective in decreasing the number of ordered intervention tests, but the combination with computer reminders did result in a large decrease of those tests. Therefore, we recommend using computer reminders in addition to education if reduction of inappropriate test use is aimed for.

Trends and variability in blood lead concentrations among US children and adolescents

Using data from the National Health and Nutrition Examination Survey for the period 2003-2012, the objective of this study was to evaluate trends in blood lead levels (BLL) among children aged 1-5 and 6-11 years and smoker and nonsmoker adolescents aged 12-19 years. Regression models with log10 transformed values of BLLs as dependent variable were fitted to evaluate how gender, race/ethnicity, smoking, and exposure to secondhand smoke at home affect BLLs. Irrespective of age, gender, and race/ethnicity, BLLs declined over the study period (p ≤ 0.01). Overall, adjusted BLLs declined by 0.00114 μg/dL for every 2 years. Children aged 1-5 years had about 50 % higher BLLs than smoker adolescents, about 75 % higher BLLs than nonsmoker adolescents, and about 45 % higher BLLs than children aged 6-11 years. While overall, children aged 1-5 years with BLL ≥ 5 μg/dL made up 3.24 %, 7.8 % non-Hispanic Black children aged 1-5 years had BLL ≥ 5 μg/dL. Males were found to have higher adjusted BLLs than females, and non-Hispanic Blacks were found to have higher adjusted BLLs than non-Hispanic Whites. Higher poverty income ratio was associated with lower adjusted BLLs (β = -0.02916, p < 0.01). Children living in owner-occupied homes had lower adjusted BLLs than children living in renter-occupied homes. BLLs increased with increase in number of smokers smoking inside the home (β = 0.02496, p = 0.02). In conclusion, while BLLs have declined for all age groups, genders, and races/ethnicities, certain races/ethnicities like non-Hispanic Blacks continue to have substantially higher BLLs than non-Hispanic Whites.

Diagnostic Utility of Angiotensin-Converting Enzyme in Sarcoidosis: A Population-Based Study

PURPOSE

Sarcoidosis is a disease with heterogenous clinical presentations. Diagnosis of sarcoidosis is often challenging with the lack of gold standard tests. In this study, we investigated the diagnostic utility of angiotensin-converting enzyme (ACE) for diagnosis of sarcoidosis.

METHODS

A cohort of Olmsted County, Minnesota residents who were diagnosed with sarcoidosis between January 1, 1984 and December 31, 2013 was identified based on individual medical record review. ACE levels recorded in the medical records of all subjects at the time of diagnosis were extracted. Comparator subjects were residents of Olmsted County, Minnesota who had ACE levels tested the same time period but did not have a diagnosis of sarcoidosis. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and the c-statistic of high versus low/normal ACE to diagnose sarcoidosis were calculated.

RESULTS

A total of 3277 Olmsted County residents age ≥18 years had at least one ACE test in 1984-2013. The sarcoidosis incidence cohort contained 295 Olmsted County residents diagnosed with sarcoidosis in 1984-2013. Of these, ACE tests were obtained in 251. The sensitivity and specificity of high ACE for diagnosis of sarcoidosis were 41.4 % (95 % CI 35.3-47.8 %) and 89.9 % (95 % CI 88.8-91.0 %), respectively. The PPV and NPV in this population were 25.4 % (95 % CI 21.3-29.9 %) and 94.9 % (95 % CI 85.0-87.4 %).

CONCLUSIONS

This study demonstrated a poor sensitivity and insufficient specificity of high ACE for diagnosis of sarcoidosis suggesting a limited role of ACE in clinical practice.

Trends in diabetes incidence among 7 million insured adults, 2006-2011: the SUPREME-DM project

An observational cohort analysis was conducted within the Surveillance, Prevention, and Management of Diabetes Mellitus (SUPREME-DM) DataLink, a consortium of 11 integrated health-care delivery systems with electronic health records in 10 US states. Among nearly 7 million adults aged 20 years or older, we estimated annual diabetes incidence per 1,000 persons overall and by age, sex, race/ethnicity, and body mass index. We identified 289,050 incident cases of diabetes. Age- and sex-adjusted population incidence was stable between 2006 and 2010, ranging from 10.3 per 1,000 adults (95% confidence interval (CI): 9.8, 10.7) to 11.3 per 1,000 adults (95% CI: 11.0, 11.7). Adjusted incidence was significantly higher in 2011 (11.5, 95% CI: 10.9, 12.0) than in the 2 years with the lowest incidence. A similar pattern was observed in most prespecified subgroups, but only the differences for persons who were not white were significant. In 2006, 56% of incident cases had a glycated hemoglobin (hemoglobin A1c) test as one of the pair of events identifying diabetes. By 2011, that number was 74%. In conclusion, overall diabetes incidence in this population did not significantly increase between 2006 and 2010, but increases in hemoglobin A1c testing may have contributed to rising diabetes incidence among nonwhites in 2011.

[Research progress on the effects of acupuncture-moxibustion serum]

The acupuncture-moxibustion serum has received wide attention as a new idea and method. Its application on researches in vivo and the treatment of disease not only has an important theory value, but also provides new ideas for overcoming the limitations of researches in vivo and some disease's treatment. Literature regarding the basic research of acupuncture-moxibustion serum for last more than 10 years is reviewed, and the effects of acupuncture-moxibustion serum on respiratory system, digestive system, cardiovascular system, nervous system, immune system, anti-aging, bone metabolism and anti-cancer are summarized, hoping to provide references for clinical treatment and evidence-based medicine.

Point-of-care technologies for molecular diagnostics using a drop of blood

Molecular diagnostics is crucial for prevention, identification, and treatment of disease. Traditional technologies for molecular diagnostics using blood are limited to laboratory use because they rely on sample purification and sophisticated instruments, are labor and time intensive, expensive, and require highly trained operators. This review discusses the frontiers of point-of-care (POC) diagnostic technologies using a drop of blood obtained from a finger prick. These technologies, including emerging biotechnologies, nanotechnologies, and microfluidics, hold the potential for rapid, accurate, and inexpensive disease diagnostics.

Patterns of preoperative laboratory testing in patients undergoing outpatient plastic surgery procedures

BACKGROUND

Preoperative laboratory testing is commonplace in the clinical setting and is often utilized at surgeon discretion. We searched the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) data set to determine the impact of preoperative laboratory testing in ambulatory plastic surgery patients.

OBJECTIVE

The authors assess the utilization and predictive value of preoperative laboratory testing in outpatient plastic surgery procedures.

METHODS

Patients undergoing ambulatory plastic surgery were identified from the 2005 to 2010 NSQIP databases. Laboratory tests were categorized by group: hematologic, chemistry, coagulation, and liver function tests (LFT). We defined complications in 2 groups: major postoperative and wound complications. Multivariate analyses were used to identify patient characteristics associated with testing and to assess the ability of laboratory testing to predict postoperative complications.

RESULTS

A total of 5359 (62.0%) patients underwent testing; 881 (16.4%) tests were performed on the day of surgery. In patients with no defined NSQIP comorbidities, 59.4% underwent preoperative testing and had a significantly lower rate of abnormal findings (33.4% vs 25.3%, P < .0001). In multivariate analyses, testing was associated with older age, American Society of Anesthesiologists class >2, Hispanic or African American race, body contouring procedures, epidural or spinal procedures, and with diabetes, hypertension, and cancer. Major complications occurred in 0.34% of patients. Our analysis demonstrated that neither testing nor abnormal results were associated with postoperative complications, either major (P = .178) or wound (P = .150).

CONCLUSIONS

We found no association between abnormal laboratory testing and postoperative morbidity. Preoperative testing in low-risk ambulatory plastic surgery patients may be costly and has limited direct clinical benefit.

Vitamin B12 and cognitive function: an evidence-based analysis

BACKGROUND

More than 2.9 million serum vitamin B12 tests were performed in 2010 in Ontario at a cost of $40 million. Vitamin B12 deficiency has been associated with a few neurocognitive disorders.

OBJECTIVE

To determine the clinical utility of B12 testing in patients with suspected dementia or cognitive decline.

METHODS

Three questions were addressed: Is there an association between vitamin B12 deficiency and the onset of dementia or cognitive decline? Does treatment with vitamin B12 supplementation improve cognitive function in patients with dementia or cognitive decline and vitamin B12 deficiency? What is the effectiveness of oral versus parenteral vitamin B12 supplementation in those with confirmed vitamin B12 deficiency? A literature search was performed using MEDLINE, Embase, EBSCO Cumulative Index to Nursing & Allied Health Literature (CINAHL), the Cochrane Library, and the Centre for Reviews and Dissemination database, from January 2002 until August 2012.

RESULTS

Eighteen studies (7 systematic reviews and 11 observational studies) were identified to address the question of the association between B12 and the onset of dementia. Four systematic reviews were identified to address the question of the treatment of B12 on cognitive function. Finally, 3 randomized controlled trials were identified that compared oral B12 to intramuscular B12.

CONCLUSIONS

Based on very low quality evidence, there does appear to be an association between elevated plasma homocysteine levels (a by-product of B vitamins) and the onset of dementia. Based on moderate quality evidence, but with less than optimal duration of follow-up, treatment with B12 supplementation does not appreciably change cognitive function. Based on low to moderate quality of evidence, treatment with vitamin B12 and folate in patients with mild cognitive impairment seems to slow the rate of brain atrophy. Based on moderate quality evidence, oral vitamin B12 is as effective as parenteral vitamin B12 in patients with confirmed B12 deficiency.

PLAIN LANGUAGE SUMMARY

Low levels of vitamin B12 have been associated with neurocognitive disorders. This evidence-based analysis assessed the usefulness of serum vitamin B12 testing as it relates to brain function. This review found very low quality evidence that suggests a connection between high plasma homocysteine levels (a by-product of B vitamin metabolism in the body) and the onset of dementia. Moderate quality of evidence indicates treatment with vitamin B12 does not improve brain function. Moderate quality of evidence also indicates treatment using oral vitamin B12 supplements is as effective as injections of vitamin B12.

Vitamin D assays: past and present debates, difficulties, and developments

Clinical interest in Vitamin D and its purported roles not only in calcium and bone metabolism but in several other medical conditions (diabetes, cardiovascular disease, multiple sclerosis, cancer, psychiatric disorders, neuro-muscular disease) has led to a surge in laboratory requests for 25 hydroxy vitamin D and 1,25 dihydroxy vitamin D measurement. Circulating 25 hydroxy vitamin D concentration is routinely used as the best indicator of vitamin D status, but measurement of other metabolites, especially the physiologically active 1,25 dihyroxy vitamin D, are of clinical value. Over the last 40 years the development of assays for vitamin D and its metabolites from early competitive binding assays through to immunoassay and liquid chromatography aligned to mass spectrometry have demonstrated various analytical challenges, the advantages and disadvantages of each method are constantly changing with new technological developments. Immunoassay remains the predominant mode of measurement for 25-hydroxy vitamin D although problems with equimolar recovery of the D2 and D3 metabolites remain an issue. Standardisation of all assays has been improved but not resolved with the currently available reference materials as evidenced by the international vitamin D external quality assurance scheme, DEQAS. The choice of method for each laboratory remains a balance mainly between turn around time, convenience, cost and the specificity and accuracy of the information obtained. With increasing discussion and clinical interest surrounding other vitamin D metabolites the vitamin D assay debate is set to continue.

Variation in prostate specific antigen (PSA) test ordering in primary care centers: tendencies 2002-2009

BACKGROUND

We aimed to compare the variation in PSA test ordering behavior between ten different health centers according to patients' age and the tendencies in PSA testing during the period of study (2002 - 2009).

METHODS

The study subjects attended 10 primary care centers in Alicante, Spain (2002 - 2009). Variables included: patient age, primary center, and year. We calculated percentages of PSA testing for each age group over the total PSA testing in each center and year.

RESULTS

A great variability has been shown between the different centers, mainly in patients where the controversy in PSA testing is higher: in the group including patients younger than 50 and those older than 85 years old. PSA testing percentages increased along the period of study for all the groups of age, except for the group of patients aged between 50 and 75 years old, where accordingly, PSA testing percentages decreased along the time.

CONCLUSIONS

These results may contribute to the discussion about the use of PSA testing and show the importance of a consensus among healthcare providers to facilitate adoption of an approach while international recommendations come to an agreement.

Proteomics meets blood banking: identification of protein targets for the improvement of platelet quality

Proteomics has brought new perspectives to the fields of hematology and transfusion medicine in the last decade. The steady improvement of proteomic technology is propelling novel discoveries of molecular mechanisms by studying protein expression, post-translational modifications and protein interactions. This review article focuses on the application of proteomics to the identification of molecular mechanisms leading to the deterioration of blood platelets during storage - a critical aspect in the provision of platelet transfusion products. Several proteomic approaches have been employed to analyse changes in the platelet protein profile during storage and the obtained data now need to be translated into platelet biochemistry in order to connect the results to platelet function. Targeted biochemical applications then allow the identification of points for intervention in signal transduction pathways. Once validated and placed in a transfusion context, these data will provide further understanding of the underlying molecular mechanisms leading to platelet storage lesion. Future aspects of proteomics in blood banking will aim to make use of protein markers identified for platelet storage lesion development to monitor proteome changes when alterations such as the use of additive solutions or pathogen reduction strategies are put in place in order to improve platelet quality for patients.

Detection and characterization of variant and modified structures of proteins in blood and tissues by mass spectrometry

Some variant proteins cause diseases, and some diseases result in increases of proteins with abnormally modified structures. The detection, characterization, and estimation of the relative amounts of protein variants and abnormally modified proteins are important for clinical diagnosis and for elucidation of the mechanisms of the pathogenesis of diseases. Analysis of the covalent structures of proteins using matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization MS (LC-ESI-MS), which had been developed by the early 1990s, have largely replaced analyses by conventional protein chemistry. Here, we review the detection and characterization of hemoglobin variants, HbA1c measurement, detection of carbohydrate-deficient transferrin, and identification of variants of transthyretin (TTR) and Cu/Zn-superoxide dismutase (SOD-1) using soft ionization MS. We also propose the diagnostic application of the signals of modified forms of TTR, that is, S-sulfonated TTR and S-homocysteinyl TTR. The relative peak height ratio of the abnormal/normal components gives valuable information about the instability of variants and enables the detection of unstable Hb subunits or thalassemia heterozygotes. We found unique modified structures of TTR that suggested changes in amyloid fibrils.

Medical applications of electronic nose technology

Electronic nose technology has been developed over the past 15 years in the field of chemistry as an electronic equivalent of the biologic mechanism of smell. Since its inception, it has been well recognized that there is great potential in applying this technology to the field of medicine. This review discusses those areas of medicine in which electronic nose technology has been applied. For each area, this review addresses the scope of the medical problem that has been studied, how the electronic nose technology may help address the medical problem, and the results of such studies to date. Next generation electronic noses will be refined to better analyze specific disease states. This will require further evaluation of the specific volatiles to be tested. This information may then be brought to bear on refinement of the chemistry of the electronic nose sensors, making them more sensitive and specific for the particular disease of interest. The ultimate goal of work in this arena is to make an electronic nose that is portable, fast, inexpensive and, therefore, suitable for use in the examination room or at the bedside, making it facile as a diagnostic tool.

Effective Use of Liquid Chromatography-Mass Spectrometry (LC/MS) in the Routine Clinical Laboratory for Monitoring Sirolimus, Tacrolimus, and Cyclosporine

The authors describe an isocratic liquid chromatographic/electrospray single quadrupole mass spectrometric assay suitable for routine therapeutic monitoring of the antirejection drugs tacrolimus, sirolimus, and cyclosporine in blood. The drugs and added internal standards, ascomycin, desmethoxysirolimus, and cyclosporine G, are extracted from a protein-free supernatant of patient blood on a Strata SDB-L styrene-divinylbenzene polymeric extraction cartridge (Phenomenex, Torrance, CA). A Gilson Aspec XL-4 (Gilson Instruments, Middleton, WI) is programmed to perform the extraction and transfer the extract to autosampler vials. The extract is automatically injected onto a C18 column held at 75 degrees C. Mobile phase, acetonitrile/water 90/10 (vol/vol), is pumped at 0.5 mL/min through a silica saturating column positioned in the column oven before the injector valve. Detection is by selected ion monitoring of the sodium adduct of each analyte, [M + 23]. A linear response is achieved for tacrolimus and sirolimus from limit of quantitation (LOQ) 1.0 microg/L to at least 80.0 microg/L. Cyclosporine was linear from LOQ 25 microg/L to at least 2000 microg/L. Interferences and ionization suppression are minimal. Analytic recovery for cyclosporine is 99.9 +/- 6.2% over a range of 104-1162 microg/L; sirolimus 107.7 +/- 9.3% over a range of 3.2-29.2 microg/L; and tacrolimus 101.9 +/- 2.5% over a range of 2.9-38.1 microg/L. Between-run relative standard deviations are 3.0% to 5.1% over a range of 9.8 microg/L to 30.7 microg/L for tacrolimus; 5.5% to 7.6% over a range of 13.5 microg/L to 35.2 microg/L for sirolimus; and 2.6% to 4.3% over a range of 186.0 microg/L to 1428.7 microg/L for cyclosporine. In the authors' laboratory, the method is robust and shows improved selectivity, precision, detection limits, and lower cost per test over available immunoassays. The authors find the method suitable for routine monitoring and therapy management of these drugs with over 50,000 samples analyzed over the course of 1 year.

The potential of biosensor technology in clinical monitoring and experimental research

Glucose or lactate biosensors are very useful for monitoring metabolism. Continuous monitoring of glucose is for example very important in diabetic patients. The measurement of lactate, a marker for oxygen deficiency, is used in the intensive care unit to monitor the patients' condition. In our laboratory we have developed two types of on-line biosensors to measure in vivo glucose and lactate: a sandwich-type biosensor and, very recently, a miniaturized flow-through biosensor. These biosensors are not placed in the body itself, but are connected to implanted microdialysis or ultrafiltration probes. Both types of biosensors are based on the oxidation of substrate using glucose oxidase or lactate oxidase and electrochemical detection. In the sandwich-type sensor, the enzymes are physically immobilized between two cellulose nitrate filters, and operate with ferrocene as a mediator. In the miniaturized biosensor, with an internal volume of 10-20 nanolitres, the enzymes are immobilized on the electrode via in situ encapsulation in poly(1,3-phenylenediamine). In this review we shall explain the working of these biosensors, and describe their application in clinical monitoring and experimental research.

Evolution of analytical performance in portable glucose meters in the last decade

OBJECTIVE

To assess and compare the technical accuracy of portable glucose meters during the last decade.

RESEARCH DESIGN AND METHODS

One-thousand preprandial (pre) and postprandial (post) capillary whole-blood glucose values measured with meters owned mainly by diabetic patients were compared with a single laboratory method yearly from 1989 to 1999. A total of 21,950 capillary measurements and their corresponding laboratory reference values were analyzed at our clinic.

RESULTS

The lowest mean absolute difference was found in 1989 (pre: 2 +/- 22 mg/dl, post: 9 +/- 31 mg/dl) (mean +/- SD). The highest mean absolute difference was observed in 1993 (pre: 31 +/- 33 mg/dl) and 1996 (post: 50 +/- 35 mg/dl). The highest mean relative deviation was observed in 1990 (pre: 16.4%) and 1996 (post: 20.6%). The highest percentage of readings that were within a 5% deviation limit were observed in 1998 (pre: 44.5%) and in 1997 (post: 36.7%). Based on blood glucose levels within +/-5 and +/-10% of laboratory values, the technical accuracy of meters was similar for 1989 and 1999 (P = 0.27 and 0.52, respectively). The percentage of pre values in zone A of Clarke's error grid analysis was >90% in 1989, 1997, 1998, and 1999.

CONCLUSIONS

The analytical performance of glucose meters decreased between 1990 and 1996 but was restored between 1997 and 1999. Nevertheless, our data suggest that the technical accuracy of glucose meters has not significantly improved during the last decade. Complementary studies taking into account the preanalytical improvements of the recent meters, as well as their calibration method, appear necessary.

Optimizing the availability of 'stat' laboratory tests using Shewhart 'C' control charts

BACKGROUND

We describe a general strategy for optimizing the availability of 'stat' out-of-hours laboratory tests to the particular clinical needs of health care institutions.

METHODS

We initially introduced a consensus menu of 'stat' tests and prospectively monitored for 5 years all additional requests for 'stat' clinical biochemistry tests in a metropolitan tertiary referral university teaching hospital. Laboratory staff triaged 'stat' requests, and clinical biochemistry consultants reviewed requests not already performed routinely. The frequency of these requests was monitored on a Shewhart 'c' control chart. A quality system certified to ISO 9001 was used to assure laboratory compliance with procedures. Various interventions were tested using the Shewhart 'c' control chart to monitor their effectiveness.

RESULTS

Matching the timing of analytical assays with the time of sample collection had no significant effect on the number of 'stat' requests. Implementation of a hospital-wide laboratory information system also had no significant effect on the number of 'stat' requests. The most effective strategy consisted of optimization of the test menu to match request patterns, combined with the introduction of a laboratory quality system.

CONCLUSIONS

Within our institution, this strategy resulted in a sevenfold reduction in 'stat' requests, from one per 2,200 specimens to fewer than one per 32,000 specimens.

The evaluation of a portable clinical analyzer in the emergency department

A recently available portable clinical analyzer (PCA), which examines sodium, potassium, chloride, glucose, urea nitrogen, and hematocrit levels on 60 microL of blood and calculates hemoglobin and osmolality levels within 2 minutes, was evaluated. Blood from 574 patients was drawn by emergency department staff, who immediately tested the samples with the PCA and transported them for plasma analysis on a reference analyzer in the clinical laboratory. Correlations between the PCA and the reference analyzer were as follows: R2 = 0.987 for urea nitrogen; R2 = 0.97, glucose; R2 = 0.937, K;R2 = 0.79, hematocrit; R2 = 0.751, sodium; and R2 = 0.689 for chloride. With its rapid turnaround, small sample requirement, and ease of operation, the PCA is most useful in an emergency department setting, where immediate access to clinically relevant laboratory testing is required in support of urgent clinical decision-making.

New whole blood analyzers and their impact on cardiac and critical care

Miniaturized whole blood biosensors, patient-focused hospitals, and rising expectations of patients and physicians are shifting laboratory diagnostics to the point of care. Expanding transplantation and intensive care are increasing the need for rapid test results. Whole blood analysis improves accuracy, eliminates centrifugation, reduces response time, and conserves blood volume. Several hand-held, and over 20 portable or transportable whole blood instruments are now available. Criteria for instrument evaluation include test menus, point-of-care features, analysis time, on-site performance, and information integration. Whole blood analyzers measure several vital indicators (pO2, pCO2, pH, hematocrit, K+, Ca2+, Na+, Cl-, glucose, and lactate) simultaneously in less than 2 min with less than 200 microliters of whole blood. Other in vitro tests are available (Mg2+, osmolality, CO2 content, urea nitrogen, beta-hydroxybutyrate, hemoglobin, coagulation) or under development (HCO3- phosphorus). Some can be monitored in vivo (O2 saturation, pO2, pCO2, pH, glucose) or ex vivo. The clinical impact is demonstrated by ionized calcium, now established in importance for cardiac and neurologic problems, and ionized magnesium, a promising new measurement. The hybrid laboratory (a composite of conventional clinical laboratory and patient-focused testing), performance maps, and quality paths facilitate implementation of new whole blood analyzers for optimal support of cardiac and critical care, and improved patient outcomes (prospects).

Current analytical approaches to measuring blood analytes

In recent years, laboratory testing in the critical-care setting has increased, a trend due, in part, to the evolution of electrochemical sensors. Various innovations have extended sensor lifetimes, reduced sensor maintenance, and led to the development of single-use and unit-use disposable sensors. These sensor technologies allow the accurate and precise determination, either at or near the bedside, of several analytes including pO2, pCO2, pH, Na, K, Cl, ionized calcium, hematocrit, total hemoglobin, and glucose. Use of these new systems, however, has raised new issues regarding sensor calibration and sample handling and collection. The number of direct-reading analyzers for electrolyte determinations has also increased dramatically. Issues regarding calibration of ion-selective electrodes (ISEs) for Na/K have also been raised after demonstrations of between-instrument variation. Recently, collaborative efforts between eight ISE instrument manufacturers and the National Institute of Standards and Technology resulted in the development of a Standard Reference Material, SRM 956, for the purpose of standardizing direct-reading Na/K ISEs to the flame photometer. Other widely used technologies that provide noninvasive, continuous monitoring include pulse oximetry and transcutaneous gas electrodes. These trends are expected to continue and to produce a new generation of electrochemical and optical sensors.