Point-of-care Testing Methods Research Articles

HbA1c-testing: Evaluation of two point-of-care analysers

BackgroundHbA1c is a critical parameter for the medical management of patients with diabetes mellitus. Interventions that reduce HbA1c levels lead to a diminution of microvascular complications. For two decades, point of care testing (POCT) methods have been regularly used to measure HbA1c. The results significantly impact on the management of patients with diabetes mellitus and the accuracy of the results is critical. It is important to know the performance of common methods of HbA1c measurements in daily life. We, therefore, aimed at evaluating the accuracy of two different analysers especially developed for POCT and compared them to a reference method. MethodsWe prospectively tested two widely used POCT methods to measure HbA1c, namely Afinion™ AS100 Analyzer (Axis-Shield, Oslo Norway) and DCA Vantage™ Analyzer (Siemens Healthcare Diagnostics, Tarrytown NY, US) in venous samples of 100 patients. As a reference method, we used the high-performance liquid chromatography method G8 HPLC used in the Biochemistry Laboratory of the Inselspital Bern. The National Glycohaemoglobin Standardization Program (NGSP) has certificated all methods used in this study. The comparability and degree of agreement was assessed using Bland–Altman plot. ResultsThe HbA1c levels ranged from 33 to 116 mmol/mol (5.2–12.8%), 31–122 mmol/mol (5.0–13.3%) and 30–119 mmol/mol (4.9–13%) for Afinion™, DCA Vantage™ and G8 HPLC Analyzer, respectively. The 95% limits of agreement were between −0.84 and +0.30 for the Afinion™ and −0.71 and +0.29 for DCA Vantage™. The results of both POCT were significantly lower with a bias of −0.27% and −0.21% (p < 0.0001) for Afinion™ and DCA Vantage™ Analyzer, respectively. ConclusionsThe POCT methods tested in this study showed a good correlation with the laboratory reference method, however, with an overall negative bias.

DIFFERENCE IN GLICATED HEMOGLOBIN LEVEL BETWEEN BORONATE AFFINITY METHOD AND ION EXCHANGE-HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD IN TYPE 2 DIABETES MELLITUS

Background: Glycated Hb (HbA1c) test is needed to control glycemic in high prevalence type 2 diabetes mellitus (DM) patients. Hemoglobin fraction separated and chemical reaction are two main concepts in HbA1c test. Ion exchange-high performance liquid chromatography (HPLC) and boronate affinity use first concept. Ion exchange-HPLC is reference method in most of clinical laboratorium. Point of care testing (POCT) with boronate affinity method that has been standardized by international institution is available. The aim of this study was to compare boronate affinity POCT method and ion exchange-HPLC method.Method: This cross sectional study was conducted to 22 type 2 DM patients those fullfill inclusion and exclusion criteria in January 2017 to February 2018. Level of HbA1c was assayed with boronate affinity POCT and ion exchange-HPLC method. T-test was used to analyse data and no significance difference if p&gt;0.005Results: Subjects of this study are women (59.1%) more than men (40.9%) with age mean 59.23 years old (8.1). Uncontroled type 2 DM (77.3%) more than controled type 2 DM (22.7%).Mean of HbA1 level was 8.0% (1.7) in boronate affinity POCT and 8.3% (1.8) in ion exchange-HPLC. T-test showed no significance difference between those two HbA1C assay methods (p&gt;0.005).Conclusion: There was no difference HbA1c level between boronate affinity POCT method and ion exchange-HPLC method.

Using a glucose meter to quantitatively detect disease biomarkers through a universal nanozyme integrated lateral fluidic sensing platform

Along with the advance in medical research, more biomarkers emerge as useful indicators for both disease and health index. However, majority of them have no practical or economic testing methods available yet, or rely on high-costing methods such as Enzyme-Linked Immuno-Sorbent Assay (ELISA), High-Performance Liquid Chromatography (HPLC), Mass Spectrum, and immunohistochemistry (IHC). In this article, we develop a universal nanozyme integrated testing platform for biological molecules that incorporates the electrochemical measurement of glucose with lateral flow immunostrip (LFS) for target analytes. This design involves the quantitative conversion of analytes into invertase and then glucose, which can be measured by an extremely affordable meter. The feasibility of this design was validated using 8-hydroxy-2’-deoxyguanosine (8-OHdG) and prostate specific antigen (PSA) as representatives for small molecules and moderate to large proteins respectively. Our approach yields results comparable to commercial diagnostic ELISA kits at a substantially reduced cost and reaction time. Specifically, the design has a detection limit of 0.23 ng mL-1 for 8-OHdG and 1.26 ng mL-1 for PSA, and a detection range of 0.1–100 ng mL-1 for 8-OHdG and 1–100 ng mL-1 for PSA. By combining the accessibility of well-established glucose testing and LFS, our design can serve as a point of care testing method that can be fully integrated into the personal lifestyle without requiring professional assistance.

Impact of Glucose Measuring Systems and Sample Type on Diagnosis Rates of Diabetes Mellitus.

IntroductionThe use of glucose point-of-care testing (POCT) devices for the diagnosis of diabetes mellitus (DM) is an ongoing controversy. In patient management, glucose concentrations are determined by POCT and core laboratory glucose methods, and the values are commonly compared even though the samples collected are different, namely, capillary whole blood and venous plasma. In individual patients it is difficult to distinguish between factors that can influence the results, such as sample type and measuring procedure. In this study, glucose concentrations obtained using POCT and core laboratory instruments were assessed to duplicate typical scenarios experienced in healthcare. Corresponding diagnosis rates of impaired glucose tolerance (IGT) and DM based on fixed, method-independent cutoffs were compared.MethodsGlucose concentration was measured by the 2-h oral glucose tolerance test (OGTT) in samples collected from an inpatient cohort and a cohort from the general population. Two POCT methods, namely, a handheld unit-use glucometer and a small bench-top analyzer with batch reagents, and two core laboratory procedures were used to measure glucose concentrations. The sample types were whole blood and plasma samples collected from venous and capillary blood. The glycated hemoglobin level in whole blood was also determined.ResultsA total of 231 subjects were included in the study. The 2-h OGTT glucose concentrations in the capillary whole blood samples showed a positive bias of 0.8 mmol/L compared to those obtained using core laboratory plasma glucose methods, leading to increased rates of diabetes diagnosis. This bias decreased to 0.2 mmol/L when venous blood was used in the tests. A change in the method used by the core laboratory introduced a negative bias of 0.5 mmol/L and, consequently, a lower diagnosis rates.Discussion and ConclusionVenous blood samples measured at the point-of-care are the most suitable sample type for the measurement of the glucose concentration in the 2-h OGTT. The investigated unit-use POCT method is suitable for the diagnosis of IGT and DM when venous blood samples are collected. Importantly, changes in measurement procedures can introduce a bias and affect diagnosis rates, thereby emphasizing the need for further harmonization of glucose methods.Plain Language SummaryA plain language summary is available for this article.Electronic supplementary materialThe online version of this article (10.1007/s13300-018-0495-0) contains supplementary material, which is available to authorized users.

Feasibility of pulse oximetry as non-invasive method for hemoglobin screening in blood donors: Evidence from a cross sectional study

Abstract Background Non-invasive point-of-care testing (POCT) devices for determining pre-donation haemoglobin (Hb) concentrations have been developed befitting the needs of blood donors and blood banks. This study was planned to evaluate the suitability of non-invasive devices over invasive POCT devices for blood donor Hb screening. Material and methods Pre-donation Hb in apparently 60 healthy blood donors was measured by a non-invasive spectrophotometric based method (pulse oximetry) and an invasive POCT method utilizing capillary blood (HemoCue). The performance of the devices was evaluated by comparison with the reference method, i.e. an automated cell counter (Sysmex). Results Hb was measured in prospective blood donors. Mean value of hemoglobin measured by HemoCue was 14.73 ± 1.20 g/dl which was more than the reference method (12.74 ± 1.23 g/dl). Moderate positive correlation was found between pulse oximetry & sodium azide method (p Conclusion Pulse-oximetry is a fast method with apparent advantage of eliminating pain. It shows adequate agreement with standard method of haemoglobin estimation but there is also a substantial possibility of causing ineligible donors to be accepted.

An ITO-based point-of-care colorimetric immunosensor for ochratoxin A detection

The accurate and rapid ochratoxin A (OTA) detection at early stage can prevent people from getting cancer to a great extent due to its strong liver toxicity and renal toxicity. The development of an efficient strategy to detect OTA without sophisticated instruments is highly desired, but still remains a severe challenge. In this communication, a sandwich type point-of-care testing (POCT) immunoassay is developed for OTA detection. The 3-aminopropyltrimethoxysilane-glutaraldehyde (APTMS-GA) is used as color matrix and Au-N-TiO2 as labels for loading more captured antibodies and glucose oxidases (GOD). When glucose is added, GOD can be catalyzed to produce H2O2 which can weaken the color strength to quantify OTA concentrations. The mean gray values of reacted ITO-based immunosensors can be calculated by the software of Image J. The linear range of OTA is 0.0001–1 ng mL–1 with a low detection limit of 28 fg mL–1 at a signal-to-noise ratio of 3 s. This strategy can achieve the excellent performance without sophisticated instruments. This POCT method may has a potential application in the undeveloped countries with only a camera-equipped cellphone.

Use of Point of Care Testing (POCT) in measurement of hemoglobin

Point of care tests (POCT) are critical to success of public health programs like anemia control program which involve measurement of biomarkers; as they help in prompt decision making during first (and in many scenario the only) contact with the targeted beneficiary. There are many methods currently in use for point of care testing for hemoglobin estimation and include manual methods like Sahli’s method, Indirect cyanmethemoglobin method, WHO Hemoglobin Color Scale method; digital hemoglobinometers including the newer non-invasive devices. The current background paper reviewed available published literature regarding performance of different POCT methods for hemoglobin estimation. Available literature indicates that invasive digital hemoglobinometers have shown a reasonable performance for use as POCT in facility and community settings both for clinical diagnosis as well as surveys. Adequate training of front line workers for use of digital hemoglobinometers and adherence to standard operating procedures (SOPs) is essential to reduce errors/biases. Non-invasive digital hemoglobinometers seem to be promising new option for POCT which obviates the need for drawing blood sample (either by venous or capillary method) but further research and development is required before their use in programs.

Development and evaluation of an up-converting phosphor technology-based lateral flow assay for the rapid, simultaneous detection of Vibrio cholerae serogroups O1 and O139.

Vibrio cholerae serogroups O1 and O139 are etiological agents of cholera, a serious and acute diarrheal disease, and rapid detection of V. cholerae is a key method for preventing and controlling cholera epidemics. Here, a point of care testing (POCT) method called Vch-UPT-LF, which is an up-converting phosphor technology-based lateral flow (UPT-LF) assay with a dual-target detection mode, was developed to detect V. cholerae O1 and O139 simultaneously from one sample loading. Although applying an independent reaction pair made both detection results for the two Vch-UPT-LF detection channels more stable, the sensitivity slightly declined from 104 to 105 colony-forming units (CFU) mL−1 compared with that of the single-target assay, while the quantification ranges covering four orders of magnitude were maintained. The strip showed excellent specificity for seven Vibrio species that are highly related genetically, and nine food-borne species whose transmission routes are similar to those of V. cholerae. The legitimate arrangement of the two adjacent test lines lessened the mutual impact of the quantitation results between the two targets, and the quantification values did not differ by more than one order of magnitude when the samples contained high concentrations of both V. cholerae O1 and O139. Under pre-incubation conditions, 1×101 CFU mL−1 of V. cholerae O1 or O139 could be detected in fewer than 7 h, while the Vch-UPT-LF assay exhibited sensitivity as high as a real-time fluorescent polymerase chain reaction with fewer false-positive results. Therefore, successful development of Vch-UPT-LF as a dual-target assay for quantitative detection makes this assay a good candidate POCT method for the detection and surveillance of epidemic cholera.

Development and Evaluation of Up-Converting Phosphor Technology-Based Lateral Flow Assay for Quantitative Detection of NT-proBNP in Blood.

A newly assay, up-converting phosphor technology-based lateral flow (UPT-LF) assay, was developed for rapid and quantitative detection of N-terminal fragment of B-type natriuretic peptide precursor (NT-proBNP), one of the most important serum molecular maker of heat failure, in plasma samples as a point of care testing (POCT) method for diagnosis of acute heart failure. Human plasma from 197 patients with acute heart failure and 200 healthy controls was assessed using the UPT-LF assay, in a comparison with a Roche Elecsys assay. The limit of detection of the UPT-LF assay, with a coefficient of variation (CV) of less than 15%, was 116 ng/L, which is lower than the clinical diagnosis cutoff (150 ng/mL). The linear range was 50–35,000 ng/L. The CVs were less than 10% for both UPT-LF and Roche Elecsys assays for plasma samples under different storages, demonstrating the good stability and reproducibility. There are certain linear correlations between the results of UPT-LF and Roche Elecsys assay for EDTA-K2 and heparin-anticoagulated plasma, as well as for serum samples. For UPT-LF assay, there is a significant correlation between the values derived from analysis of EDTA-K2 and heparin-anticoagulated plasma samples (R = 0.995). No statistically significant difference was found between serum and plasma samples for UPT-LF assay. Our results demonstrate that NT-proBNP levels in healthy adults are elevated with age and had a relationship with sex, and with the age increase the NT-proBNP levels of females are significantly higher than those of males (p<0.01). The UPT-LF assay has a high reproducibility, stability, sensitivity, specificity, and is consistent with Roche Elecsys assay, and therefore it could be used as a POCT method for the quantitative detection of NT-proBNP in blood for clinical diagnosis and research of acute heart failure.

Evaluation of Point of Care Test (POCT), i-CHROMA™ Serum C-Reactive Protein (CRP) Assay and Microalbumin Urine (MAU) Methods

Objectives: The objective of this study was to evaluate the performance of the Boditech i-CHROMA™ point-of-care testing (POCT) method for the quantification of serum CReactive Protein (CRP) and Urine Microalbumin (MAU) compared well with the traditional Abbott Architect Ci8200 laboratory method. Design and Methods: Serum samples of CRP (n=44) and urine samples for MAU estimation (n=25) were analysed at the Homerton University Hospital using the routine laboratory method (Abbott Architect Ci8200) and the Boditech i-CHROMA™ POCT method. Results: The i-CHROMA™ CRP and MAU method showed good correlation with that of the Abbott Architect Ci8200: r2=0.905 and r2=0.987 respectively. Overall, there was a slight negative bias seen with the i-CHROMA™ CRP method (bias=-8.15, bias difference=-9.05%) and a negative bias seen with the i-CHROMA™ MAU method (bias=35.84, bias difference=-27.88%). Conclusion: The Boditech i-CHROMA™ POCT method provide a reliable measurement of CRP and MAU and compared well with the traditional Abbott Architect Ci8200 laboratory method.

Noninvasive hemoglobin measurement in pediatric trauma patients.

Hemorrhage is a major cause of preventable death secondary to traumatic injury. Diagnosis often requires multiple blood draws, which are psychologically stressful in pediatric patients. The Pronto device is a pulse co-oximeter that measures the total hemoglobin level using multiple wavelengths of light. The purpose of this study was to evaluate the accuracy of the noninvasive hemoglobin measurements relative to current invasive and point of care testing methods in pediatric trauma patients. We performed a prospective observational trial involving patients younger than 17 years presenting to a Level I pediatric trauma center. Following admission, blood was sampled from each patient for testing using an i-Stat device (point-of-care hemoglobin) and a complete blood count within our core laboratory (invasive hemoglobin). Noninvasive hemoglobin analysis was performed within 15 minutes of phlebotomy. Data were evaluated using Spearman correlation and Bland-Altman analysis. Over 2 years, 114 patients had attempted noninvasive hemoglobin measurements, with a success rate of 89%. Mean ± SD age was 9.2 ± 5.1 years. Ninety percent of admissions were for blunt injury, 3% penetrating, 5% near drowning, and 1% burns. Mean invasive hemoglobin was 12.6 ± 1.9 g/dL, mean point-of-care hemoglobin was 12.2 ± 2.0 g/dL, and mean noninvasive hemoglobin was 12.3 ± 1.6 g/dL. Noninvasive hemoglobin values were strongly correlated with both invasive and point of care measurements (R = 0.672 and R = 0.645, respectively; p < 0.001). Bland-Altman analysis comparing noninvasive to point-of-care and invasive hemoglobin levels resulted in an estimated bias of -0.39 and -0.49, respectively. Noninvasive hemoglobin values had excellent correlation with both invasive and point-of-care hemoglobin measurements, although the device was not successful for all patients. Given the rapid availability of results and the lack of requirement of venipuncture, noninvasive hemoglobin monitoring may be a valuable adjunct in the initial evaluation and monitoring of pediatric trauma patients. Diagnostic test study, level II.

Development and evaluation of an up-converting phosphor technology-based lateral flow assay for rapid detection of Francisella tularensis.

Francisella tularensis is a potential biowarfare/bioterrorism agent and zoonotic pathogen that causes tularemia; thus, surveillance of F. tularensis and first-level emergency response using point-of-care testing (POCT) are essential. The UPT-LF POCT assay was established to quantitatively detect F. tularensis within 15 min, and the sensitivity of the assay was 104 CFU · mL−1 (100 CFU/test). The linear quantitative range covered five orders of magnitude, and the coefficients of variation were less than 10%. Except Shigella dysenteriae, UPT-LF showed excellent specificity to four strains that are also potential biowarfare/bioterrorism agents and 13 food-borne pathogenic strains. Samples with pH 2–13, high ion strengths (≥2 mol · L−1 solution of KCl and NaCl), high viscosities (≤50 mg · mL−1 PEG20000 or ≥20% glycerol), and high concentrations of biomacromolecules (≥400 mg · mL−1 bovine serum albumin or ≥80 mg · mL−1 casein) showed little influence on the assay. For practical utilization, the tolerance limits for seven powders and eight viscera were determined, and operation errors of liquid measurement demonstrated a minor influence on the strip. Ftu-UPT-LF is a candidate POCT method because of its excellent sensitivity, specificity, and stability in complex samples, as well as low operation error.

Falsely Elevated Glucose Concentrations in Peritoneal Dialysis Patients Using Icodextrin.

Peritoneal dialysis (PD) is used as an alternative to hemodialysis in end-stage renal disease (ESRD). Icodextrin has been used as a hyperosmotic agent in PD. The aim of the study was to assess two different point-of-care testing (POCT) glucose strips, affected and not affected by icodextrin, with serum glucose concentrations of the patients using and not using icodextrin. Fifty-two chronic ambulatory peritoneal dialysis (CAPD) patients using icodextrin (Extraneal®) and 20 CAPD patients using another hyperosmotic fluid (Dianeal®) were included in the study. Duplicate capillary and serum glucose concentrations were measured with two different POCT glucose strips and central laboratory hexokinase method. Assay principles of glucose strips were based on glucose dehydrogenase-pyrroloquinoline quinone (GDH-PQQ) and a mutant variant of GDH (Mut Q-GDH). The results of both strips were compared with those of hexokinase method. Regression equations between POCT and hexokinase methods in icodextrin group were y = 2.55x + 1.12 mmol/l and y = 1.057x + 0.16 mmol/l for the GDH-PQQ and Mut Q-GDH methods, respectively. The mean difference between the results of hexokinase and those of GDH-PQQ and Mut Q-GDH in icodextrin group was 3.41 ± 1.56 and 0.72 ± 0.64 mmol/l, respectively. However, the mean differences were found much lower in the control group; 0.64 mmol/l for GDH-PQQ and 0.52 mmol/l for Mut Q-GDH. Compared to GDH-PQQ, glucose strips of Mut Q-GDH correlated better with hexokinase method in PD patients using icodextrin.

Therapeutic monitoring of benzodiazepines in the management of pain: Current limitations of point of care immunoassays suggest testing by mass spectrometry to assure accuracy and improve patient safety

BackgroundConcomitant use of opioids and benzodiazepines can result in significant untoward effects. Point of care (POC) urine testing devices are commonly used tools to monitor patient use of medications. These useful devices are relatively inexpensive and yield immediate results that can be acted upon at the time of the appointment, although numerous limitations have been identified for specific medications or medication classes. We established the diagnostic accuracy of a commonly used POC testing method for benzodiazepines. MethodsOne thousand patients, from a single interventional pain practice receiving opioid therapy provided urine specimens as part of the usual practice of monitoring consistency with prescribed medications. These de-identified urine specimens were tested using LC-MS/MS and the results were compared using the standard calculations for sensitivity, specificity, and predicted value. Five specimens were excluded from the study because the prescribed flurazepam could not be confirmed by LC-MS/MS (the LC-MS/MS instrumentation was not set to identify flurazepam), resulting in 995 specimens. ResultsPoint of care assays yielded false negative results for patients prescribed benzodiazepines nearly 20% of the time (98 out of 498 patients). The point of care cup often failed to produce positive results for persons who were shown by LC-MS/MS to be taking lorazepam or clonazepam. Although only 26 out of 498 patients (5%) were prescribed ≥2 benzodiazepines, 73 out of 498 patients (15%) were found to be positive for that drug class. ConclusionsPOC immunoassay for benzodiazepines could fail to provide accurate information regarding patient specific medication use. The false positive and false negative rates of the immunoassay were particularly high for clonazepam and lorazepam. Further testing of patient specimens using more accurate methods such as LC-MS/MS is necessary to provide definitive data that can assist in clinical decision making, and potentially protect these patients from untoward effects, morbidity and mortality.

Point-of-Care Testing Quality: Some Positives but Also Some Negatives

Point-of-care testing (POCT)2 represents one of the fastest growing segments of the diagnostics market. Although major advances have been made in the instrumentation and methods used for POCT, further development and enhancements appear to be necessary to meet the challenges presented by the difficult testing environments in which these devices are used. In addition, the varied experience and training of users and their use of samples that may not be optimal for testing continue to present challenges in the implementation of POCT (1). One of the major advantages of POCT is that it provides much faster access to test results, allowing for more rapid clinical decision making and more-appropriate treatments and interventions. In addition, POCT can help minimize time-dependent changes in labile analytes such as lactate and glucose, which can be caused by delays in sample transport to the clinical laboratory. Finally, many POCT methods require much smaller sample volumes than those needed for testing in the central clinical laboratory. Preventing medical errors has become a major focus of quality improvement in healthcare. Most errors that occur in the clinical laboratory setting take place during the pre- and postanalytical phases of the testing process, and several studies have documented the types and frequencies of the errors that can occur (2). In addition to the benefits mentioned above, the use of POCT may help reduce the frequencies of some of these errors, such as the preanalytical errors associated with inappropriate sampling, inappropriate preparation or packaging of samples, and misidentification of patients (3). In addition, the …

Urinary Measurement of N-Terminal B Type Natriuretic Peptide in Patients With Cardiac Failure - Highway or Byway?

Urine testing has the advantage of being convenient, familiar to a range of healthcare professionals, and non-invasive. Urine testing for albumin has a well-established role in the management of the diabetic patient and the assessment of renal disease. Urinary measurement of N-terminal B type natriuretic peptide (NTproBNP) has been proposed as a potential tool for detection of cardiac failure. Such an approach would be ideally suited for communitybased diagnosis and potentially useful for the emergency department. Point of care testing (POCT) is already available for measurement of both B type natriuretic peptide (BNP) and NTproBNP in whole blood. If a POCT method for NTproBNP measurement in urine could be developed it could provide a convenient, simple test for heart failure. The clinical diagnosis of heart failure is notoriously difficult. In a systematic review comparing clinical symptoms and signs, the electrocardiogram, and chest radiography, the poor diagnostic efficiency of clinical symptoms and signs was demonstrated and the diagnostic superiority of natriuretic peptide measurements confirmed. 1 It has been estimated that 30%-60% of referrals from primary to secondary care for investigation of suspected heart failure are subsequently found to be inappropriate. A strategy to reduce inappropriate referrals with suspected heart failure would therefore be invaluable, especially in the prevailing climate of scarce healthcare resources. If inappropriate referrals could be reduced by urine POCT for NTproBNP there would be a strong argument on the basis of cost economics to utilize such a test. The cost efficiency of ruling out heart failure using serum B type natriuretic peptide measurement has already been demonstrated. 2

Evaluation of First-Draw Whole Blood, Point-of-Care Cardiac Markers in the Context of the Universal Definition of Myocardial Infarction: A Comparison of a Multimarker Panel to Troponin Alone and to Testing in the Central Laboratory

Previous studies evaluating point-of-care testing (POCT) for cardiac biomarkers did not use current recommendations for troponin cutoff values or recognize the recent universal definition of acute myocardial infarction. Traditionally, achieving optimal sensitivity for the detection of myocardial injury on initial presentation required combining cardiac troponin and/or creatine kinase isoenzyme MB with an early marker, usually myoglobin. In recent years, the performance of central laboratory combining cardiac troponin assays has improved significantly, potentially obviating the need for a multimarker panel to achieve optimum sensitivity. To compare 2 commonly used POCT strategies to a fourth generation, central laboratory cardiac troponin T assay on first-draw specimens from patients being evaluated for acute myocardial infarction in the emergency department. The 2 strategies included a traditional POCT multimarker panel and a newer POCT method using cardiac troponin I alone. Blood specimens from 204 patients presenting to the emergency department with signs and/or symptoms of myocardial ischemia were measured on the 2 POCT systems and by a central laboratory method. The diagnosis for each patient was determined by retrospective chart review. The cardiac troponin T assasy alone was more sensitive for acute myocardial infarction than the multimarker POCT panel with equal or better specificity. When compared with a POCT troponin I, the cardiac troponin T was also more sensitive, but this difference was not significant. The POCT troponin I alone also had the same sensitivity as the multimarker panel. Testing for combining cardiac troponin alone using newer, commercially available, central laboratory or POCT assays performed with equal or greater sensitivity to acute myocardial infarction as the older, traditional, multimarker panel. In the near future, high-sensitivity, central laboratory troponins will be available for routine clinical use. As a result, the quality gap between central laboratories and older POCT methods will continue to widen, unless the performance of the POCT methods is improved.

Point-of-care determination of neonatal bilirubin with the blood gas analyzer RapidLab 1265

The aim of the study was to evaluate the comparability of the new neonatal bilirubin method on the RapidLab 1265 blood gas analyzer. This point-of-care testing (POCT) device has the option for the determination of neonatal bilirubin, making it potentially valuable for use in neonate intensive care units or in outpatient ambulances. We paired 240 patient samples for intermethod comparisons between the new POCT method and the routine laboratory method (Vitros 350 chemistry system with BuBc slide). In parallel, a transcutaneous jaundice meter (JM-103) was applied to the newborns. Low birthweight and premature neonates were excluded from the trial. The turn-around-time (TAT) for the POCT method was also compared with the routine method, and the practicality of the new analyzer was evaluated for clinical purposes. Bilirubin measurements using the RapidLab 1265 are suitable for the application in newborns. For imprecision, coefficients of variation between 5.6% and 23% were found. The correlation between the Vitros 350 (x) and RapidLab 1265 (y) was y=1.0x-0.1 (r=0.91), with a mean bias of +0.1 mg/dL and a 95% limit of agreement of ±2.5 mg/dL. As in all POCT methods, the TAT was significantly lower than that of the core laboratory. In contrast to the JM-103, the results of the RapidLab 1265 correlated closely with the Vitros 350, although occasional results of both methods were more different than expected. In general, the RapidLab 1265 blood gas analyzer provides clinically useful bilirubin results using neonatal whole blood samples, although imprecision data are higher than for the laboratory method. The POCT device is suitable for neonatal intensive care units after thoroughly training the employees that will use the device.

Interference in a Glucose Dehydrogenase–Based Glucose Meter

The US Food and Drug Administration (FDA)1 has issued a second alert to warn of serious errors with certain blood glucose–monitoring strips that use glucose dehydrogenase pyrroloquinoline quinine (GDH-PQQ) methods (1). Various nonglucose sugars, including maltose, galactose, and xylose, increase the glucose concentrations reported by these methods. Nonglucose sugars are present in a variety of pharmaceutical preparations(1), including Extraneal (icodextrin) peritoneal dialysis solution(2) and various immunoglobulin preparations(3). At least 13 deaths associated with erroneous meter measurements of glucose in patients receiving such pharmaceutical preparations have been reported to the FDA. A 76-year-old man at our institution had 3 blood glucose readings that unexpectedly were >22.2 mmol/L (>400 mg/dL) on a point-of-care (POC) testing meter that used a GDH-PQQ method (Roche Accu-Chek Inform). By contrast, glucose measurements made with a hexokinase method (Abbott Architect) at about the same times were in the range of 7.2–11.2 mmol/L (129–202 mg/dL), suggesting the possibility of a positive interference in the POC method. The patient’s medication list contained none of the pharmaceutical preparations listed in the FDA alert as producing interference in the POC testing method and none that were known to contain nonglucose sugars. In a search for other sources of interfering compounds that might contribute to this patient’s high …

Patient safety and sources of error in point-of-care testing / Patientensicherheit und Fehlerquellen in patientennaher Labordiagnostik

Abstract Patient safety is the project of reducing medical errors by creating and enforcing standards of practice, tracking and publishing errors to guide countermeasures, improving information transfer, and fostering increased accountability among healthcare providers. Errors in point-of-care testing (POCT) can be practical, cognitive, or axiological (the latter are errors of judgment). Countermeasures to errors in POCT have been organized into a laboratory ethos of test operator training and competence demonstration, explicit written procedures, routine quality control, recorded, verified, and retrievable patient results, and external proficiency testing. Three characteristics of POCT can defeat these countermeasures: technical limitations of POCT methods, the rapid availability of their results, and the tendency of these results to change patient care immediately. In the United States, government regulations of POCT have not been a success, but government mandated accreditation programs have been more effective. Laboratorians who monitor of POCT – called in the United States point-of-care test coordinators – have been essential to reporting and tracking POCT errors. They have exploited electronic information transfer to do so and to increase accountability for POCT among clinician test operators. Although a modified version of Gerald Kost's taxonomy of sources of errors offers a systematic approach to POCT error classification, major preventable adverse events (called “sentinel events” in the United States) tend to drive POCT patient safety. This circumstance has stressed the importance of clinical contexts. Tight glycemic control using POCT whole blood glucose is the example with which we illustrate the challenges to patient safety, from the technical limitations, rapid result availability, and impact on therapy, characteristic of POCT.