International Organization For Standardization Criteria Research Articles

Real-Time Continuous Glucose Monitoring in an Intensive Care Unit: Better Accuracy in Patients with Septic Shock

This study assessed the accuracy of real-time continuous glucose monitoring system (RTCGMS) devices in an intensive care unit (ICU) to determine whether the septic status of the patient has any influence on the accuracy of the RTCGMS. In total, 41 patients on insulin therapy were included. Patients were monitored for 72 h using RTCGMS. Arterial blood glucose (ABG) samples were obtained following the protocol established in the ICU. The results were evaluated using paired values (excluding those used for calibration) with the performance assessed using numerical accuracy. Nonparametric tests were used to determine statistically significant differences in accuracy. In total, 956 ABG/RTCGMS pairs were analyzed. The overall median relative absolute difference (RAD) was 13.5%, and the International Organization for Standardization (ISO) criteria were 68.1%. The median RADs reported for patients with septic shock, with sepsis, and without sepsis were 11.2%, 14.3%, and 16.3%, respectively (P<0.05). Measurements meeting the ISO criteria were 74.5%, 65.6%, and 63.7% for patients with septic shock, with sepsis, and without sepsis, respectively (P<0.05). The results showed that the septic status of patients influenced the accuracy of the RTCGMS in the ICU. Accuracy was significantly better in patients with septic shock in comparison with the other patient cohorts.

Clinical outcomes of cataract surgery after bag-in-the-lens intraocular lens implantation following ISO standard 11979-7:2006

To assess the clinical outcomes of bag-in-the-lens intraocular lens (BIL IOL) implantation following the International Organization for Standardization (ISO) 11979-7:2006 in pediatric eyes and eyes with ocular comorbidities. Antwerp University Hospital, Department of Ophthalmology, Antwerp, Belgium. Cohort study. This cohort included the first series of patients having IOL implantation using the bag-in-the-lens technique. Surgeries were performed between December 1999 and September 2006. In addition to IOL implantation, the technique comprised creation of a primary posterior continuous curvilinear capsulorhexis (PCCC) equal in size to the anterior capsulorhexis. The study enrolled 807 eyes of 547 patients; 326 of the eyes (40.40%) had ocular comorbidity. In the 481 eyes without ocular comorbidity, the mean decimal corrected distance visual acuity was 0.52 ± 0.24 (SD) (0.276 ± 0.206 logMAR) preoperatively and 0.94 ± 0.18 (-0.012 ± 0.053 logMAR) postoperatively. The mean postoperative achieved spherical equivalent was 0.48 ± 0.83 diopter (D) and the mean targeted refraction, -0.24 ± 0.71 D. The A-constant was modified from 118.4 to 118.04. Posterior capsule opacification (PCO) did not occur in any adult eye during the follow-up. Retinal detachment after IOL implantation occurred in 10 eyes (1.24%). In 19 eyes, the iris was captured by the IOL haptics postoperatively. Hypopyon occurred in 3 patients and toxic anterior segment syndrome in 1 patient. The BIL IOL met the ISO criteria; that is, primary PCCC was safe in healthy eyes and in eyes with ocular comorbidities and no eye developed PCO over a mean follow-up of 26.1 ± 21.3 months.

Intravascular Microdialysis as a Method for Measuring Glucose and Lactate during and after Cardiac Surgery

The aim was to evaluate intravascular microdialysis as a method for measuring blood glucose and lactate in a clinical setting during and after cardiac surgery. Ten patients undergoing cardiac surgery were included. A microdialysis catheter was percutaneously placed in the superior vena cava or right atrium. Glucose and lactate values measured by the microdialysis technique were analyzed and compared with reference methods, i.e., arterial and venous blood gas values, once every hour up to 24 hours postoperatively. Laboratory plasma glucose was additionally analyzed every 4 hours for reference value. Mean absolute differences were low between microdialysis and reference methods for both glucose and lactate values. All microdialysis glucose values were in the clinically acceptable zone of error grid analysis when compared with plasma glucose values. Accuracy of glucose values was 92% according to International Organization for Standardization criteria. Intravascular microdialysis is a novel and promising technique for real-time and accurate measurement of glucose and lactate during and after open heart surgery. Development of sensor technology may allow for continuous measurement of blood glucose and lactate using intravascular microdialysis.

Accuracy and reliability of a subcutaneous continuous glucose-monitoring system in critically ill patients*

Continuous glucose monitoring has been proposed to optimize glucose control in critically ill patients. To achieve strict glucose regulation, accurate and reliable continuous glucose-monitoring systems are essential. Evaluation of a subcutaneous continuous glucose-monitoring system for use in critically ill patients. Pooled-data analysis of two prospective, randomized, controlled trials. An eight-bed medical intensive care unit of a university hospital. A total of 174 critically ill patients on intensive insulin therapy. Subcutaneous continuous glucose monitoring. Two thousand forty-five continuous glucose-monitoring system sensor glucose values were compared with arterial reference blood glucose levels, determined by a blood gas analyzer. Continuous glucose monitoring data were recorded continuously for up to 72 hrs by using a subcutaneous continuous glucose-monitoring sensor. The correlation of both methods and differences between continuous glucose-monitoring systems and reference values were calculated, as well as the conformity of continuous glucose-monitoring values with the International Organization for Standardization criteria (<0.83 mmol/L [15 mg/dL] difference for glucose values ≤ 4.12 mmol/L [≤ 75 mg/dL] and <20% difference for glucose values >4.12 mmol/L [>75 mg/dL]). The Pearson correlation coefficient was 0.92, showing strong correlation between the two methods. The intraclass correlation coefficient was 0.92, indicating that 92% of the variability is due to subjects and measurement occasions. Mean difference between continuous glucose-monitoring system and reference values was -0.10 mmol/L (confidence interval: -0.13 to -0.07) (-2 mg/dL [confidence interval: -2 to -1]) (continuous glucose-monitoring system minus reference) and absolute difference 0.44 mmol/L (confidence interval: 0.41-0.47) (8 mg/dL [confidence interval: 7-8]). According to the insulin titration error grid analysis, 99.1% of continuous glucose-monitoring system values were in the acceptable treatment zone. No continuous glucose-monitoring system measurements were found in the life-threatening zone, and 92.9% of the continuous glucose-monitoring system glucose values met the International Organization for Standardization criteria. The subcutaneous continuous glucose-monitoring system is reliable for use in critically ill patients and showed glucose values with a strong correlation to arterial reference blood glucose levels, determined by a blood gas analyzer.

The Accuracy of Home Glucose Meters in Hypoglycemia

Home glucose meters (HGMs) may not be accurate enough to sense hypoglycemia. We evaluated the accuracy and the capillary and venous comparability of five different HGMs (Optium Xceed [Abbott Diabetes Care, Alameda, CA, USA], Contour TS [Bayer Diabetes Care, Basel, Switzerland], Accu-Chek Go [Roche Ltd., Basel, Switzerland], OneTouch Select [Lifescan, Milpitas, CA, USA], and EZ Smart [Tyson Bioresearch Inc., Chu-Nan, Taiwan]) in an adult population. The insulin hypoglycemia test was performed to 59 subjects (56 males; 23.6 +/- 3.2 years old). Glucose was measured from forearm venous blood and finger capillary samples both before and after regular insulin (0.1 U/kg) was injected. Venous samples were analyzed in the reference laboratory by the hexokinase method. In vitro tests for method comparison and precision analyses were also performed by spiking the glucose-depleted venous blood. All HGMs failed to sense hypoglycemia to some extend. EZ Smart was significantly inferior in critical error Zone D, and OneTouch Select was significantly inferior in the clinically unimportant error Zone B. Accu-Chek Go, Optium Xceed, and Contour TS had similar performances and were significantly better than the other two HGMs according to error grid analysis or International Organization for Standardization criteria. The in vitro tests were consistent with the above clinical data. The capillary and venous consistencies of Accu-Chek Go and OneTouch Select were better than the other HGMs. The present results show that not all the HGMs are accurate enough in low blood glucose levels. The patients and the caregivers should be aware of these restrictions of the HGMs and give more credit to the symptoms of hypoglycemia than the values obtained by the HGMs. Finally, these results indicate that there is a need for the revision of the accuracy standards of HGMs in low blood glucose levels.

Real-Time Glucose Estimation Algorithm for Continuous Glucose Monitoring Using Autoregressive Models

Continuous glucose monitors (CGMs) present a problem of lack of accuracy, especially in the lower range, sometimes leading to missed or false hypoglycemia. A new algorithm is presented here aimed at improving the measurement accuracy and hypoglycemia detection. Its core is the estimation of blood glucose (BG) in real time (RT) from CGM intensity readings using autoregressive (AR) models. Eighteen patients with type 1 diabetes were monitored for three days (one at the hospital and two at home) using the CGMS Gold. For these patients, BG samples were taken every 15 min for 2 h after meals and every half hour otherwise during the first day. The relationship between the current measured by the CGMS Gold and BG was learned by an AR model, allowing its RT estimation. New capillary glucose measurements were used to correct the model BG estimations. A total of 563 paired points were obtained from BG and monitor readings to validate the new algorithm. 98.5% of paired points fell in zones A+B of the Clarke error grid analysis with the proposed algorithm. The overall mean and median relative absolute differences (RADs) were 9.6% and 6.7%. Measurements meeting International Organization for Standardization (ISO) criteria were 88.7%. In the hypoglycemic range, the mean and median RADs were 8.1% and 6.0%, and measurements meeting ISO criteria were 86.7%. The sensitivity and specificity with respect to hypoglycemia detection were 91.5% and 95.0%. The performance measured with both clinical and numerical accuracy metrics illustrates the improved accuracy of the proposed algorithm compared with values presented in the literature. A significant improvement in hypoglycemia detection was also observed.

Accuracy of bedside glucose measurement from three glucometers in critically ill patients*

Implementation of strict glucose control in most intensive care units has resulted in increased use of point-of-care glucose devices in the intensive care unit. The aim of this study was to determine the reliability of point-of-care testing glucose meters among critically ill patients under intensive insulin treatment. Prospective observational study. Intensive care unit and non-intensive care unit patients in a tertiary care teaching hospital. A glucose oxidase method was used to validate the point-of-care testing devices. Three different point-of-care testing devices, Accu-Chek Sensor (Roche Diagnostics), Precision (Abbott Diagnostics), and HemoCue were tested. Glucose measurements were performed in duplicate by an experienced technician under standardized conditions in the hospital's laboratory, using arterial (intensive care unit patients) and arterial or venous (non-intensive care unit patients) heparinized whole blood samples. A strong correlation was found between the glucose oxidase method and the Accu-Chek device (r = .9596, p < 0.001). Mean absolute difference between the glucose oxidase and Accu-Chek was -0.32 mmol/L (95% confidence interval -0.84 to 1.48 mmol/L). Using the International Organization for Standardization (ISO) criteria, 27 of 197 samples (13.7%) were inaccurate. In all samples that failed to meet the ISO criteria, glucose values measured by the Accu-Chek device were higher compared with the glucose oxidase method. In another set of experiments among intensive care unit patients, strong positive correlations were also found between the other point-of-care testing devices and the glucose oxidase method. However, paired samples from Accu-Chek, HemoCue, and Precision failed the ISO criteria in 9 of 82 (11.0%), 4 of 82 (4.9%), and 11 of 82 (13.4%) of cases, respectively. In non-intensive care unit patients paired samples from Accu-Chek, HemoCue, and Precision failed the ISO criteria in 3 of 120 (2.5%), 11 of 120 (9.2%), and 16 of 120 (13.3%) cases, respectively. Under standardized conditions, glucose results from three point-of-care testing devices were inaccurate in both intensive care unit and non-intensive care unit patients. Among intensive care unit patients, inaccurate glucose readings were most frequently falsely elevated, resulting in misinterpretation of high glucose values with subsequent inappropriate insulin administration or masking of true hypoglycemia.

Results of the performance verification of the CoaguChek XS system

Background This is the first paper reporting a performance verification study of a point-of-care (POC) monitor for prothrombin time (PT) testing according to the requirements given in chapter 8 of the International Organization for Standardization (ISO) 17593:2007 standard “ Clinical laboratory testing and in vitro medical devices — Requirements for in vitro monitoring systems for self-testing of oral anticoagulant therapy”. The monitor under investigation was the new CoaguChek XS system which is designed for use in patient self testing. Its detection principle is based on the amperometric measurement of the thrombin activity generated by starting the coagulation cascade using a recombinant human thromboplastin. Methods The system performance verification study was performed at four study centers using venous and capillary blood samples on two test strip lots. Laboratory testing was performed from corresponding frozen plasma samples with six commercial thromboplastins. Samples from 73 normal donors and 297 patients on oral anticoagulation therapy were collected. Results were assessed using a refined data set of 260 subjects according to the ISO 17593:2007 standard. Results Each of the two test strip lots met the acceptance criteria of ISO 17593:2007 versus all thromboplastins (bias − 0.19 to 0.18 INR; > 97% of data within accuracy limits). The coefficient of variation for imprecision of the PT determinations in INR ranged from 2.0% to 3.2% in venous, and from 2.9% to 4.0% in capillary blood testing. Capillary versus venous INR data showed agreement of results with regression lines equal to the line of identity. Conclusion The new system demonstrated a high level of trueness and accuracy, and low imprecision in INR testing. It can be concluded that the CoaguChek XS system complies with the requirements in chapter 8 of the ISO standard 17593:2007.

Evaluation of a New Blood Glucose Monitoring System with Auto-Calibration

The Ascensia CONTOUR System (Bayer HealthCare LLC, Elkhart, IN) is a new blood glucose (BG) monitoring system (BGMS) that uses glucose dehydrogenase chemistry and that combines low sample volume, fast response time, an auto-control marking feature, and an auto-calibration function in a small package. The system was evaluated at four diabetes clinics with ambulatory subjects who had diabetes. The BGMS was tested by both health care professionals (HCPs) and lay users. It was also evaluated at high altitude (10,200 feet) and, in conjunction with the Ascensia MICROLET VACULANCE (Bayer), for use with samples obtained from four alternative anatomical sites. When the system was used with blood from fingersticks, both lay users and HCPs obtained results that fulfilled the International Organization for Standardization (ISO) 15197:2003 accuracy criteria, which advocate that 95% of BG measurements should fall within +/-15 mg/dL (for BG concentrations <75 mg/dL) or +/-20% (for BG concentrations > or = 75 mg/dL) of the laboratory value. Lay users obtained 96.9% of glucose results, and HCPs obtained 96.4% of glucose results, within ISO accuracy criteria. People with diabetes who had no prior experience using the system also obtained acceptable results (97.0%), as did the HCP using fingerstick samples from subjects in the high altitude study (97.0%). Among the alternative anatomical sites tested, only the results from the palm met the ISO criteria (97.5%), although the results from all four sites (palm, thigh, abdomen, and forearm) were clinically acceptable when assessed using error grid analysis. Most subjects rated the BGMS as either excellent or very good in a questionnaire, and were able to use it properly without training. These findings indicate that the Ascensia CONTOUR System, which does not require calibration by the user, is a convenient and accurate instrument with useful features for people who routinely monitor BG.