Reflectance Meter Research Articles

A questionnaire study into the use of blood glucose reflectance meters by general practice staff

AbstractAn audit of the use of blood glucose reflectance meters by staff working in 39 general practices. Questions focused on training in the use of meters; health, safety and legal implications of producing results by meters; and whether practices were employing internal or external quality assessments to monitor the results obtained.Results highlighted varied sources of training. Only a minority of practices had actively addressed health, safety and legal implications in the use of meters. The survey revealed that three practices employed internal quality control. No practices were using external quality assessments.

Reflectance meter with high spatial resolution and its application for a surface emitting laser diode

A reflectance meter with high spatial resolution is realized with a Ti–sapphire tunable laser as a light source. The spot size of an incident beam is 2 μm when an objective lens with the power of 20 was employed. The reflectivity of the optical cavity for a surface emitting laser diode (SELD) and its change with carrier injection was measured. The gain and refractive index variation of the active layer in the SELD was estimated by the parameter fitting based on a simple Fabry–Perot cavity model with material loss.

Screening for diabetes mellitus in adults. The utility of random capillary blood glucose measurements.

Because half of the people with non-insulin-dependent diabetes mellitus (NIDDM) are undiagnosed and because near-normal glycemic control can prevent diabetic complications, we evaluated the use of field-based random capillary blood glucose measurement as a screening test for NIDDM. A cross-sectional sample of 828 Egyptians > or = 20 years of age underwent both a random capillary blood glucose measurement performed with a portable reflectance meter in the field and an oral glucose tolerance test in the laboratory. The sensitivity and specificity of random capillary blood glucose measurements in predicting the presence of NIDDM were evaluated. Multivariate analyses showed that the screening test performed better when subjects had eaten shortly before the test (area under receiver operating characteristic curve, 0.87 for a 1-h postprandial period compared with 0.69 for an 8-h postprandial period) and that the optimal capillary blood glucose cutoff points to define a positive test increased with age. For a postprandial period of 1 h, cutoff points of 115 mg/dl for individuals 30 years of age and 140 mg/dl for those 75 years of age yielded similar performance characteristics (sensitivity 82% and specificity 78% for those 30 years old; sensitivity 81% and specificity 80% for those 75 years old). Adjusting random capillary blood glucose measurements for the postprandial period and using age-specific cutoff point values can improve performance of the screening test.

Effect of N‐acetylcysteïne on photofrin‐induced skin photosensitivity in patients

One of the major side effects of photodynamic therapy (PDT) employing Photofrin as the sensitizer is enhanced photosensitivity of the skin. The basic mechanism in PDT damage is believed to be the formation of singlet oxygen and radical species. N-acetylcysteïne (NAC) increases glutathione levels and is known to prevent pathology elicited by radicals and reactive species. NAC was tested in a randomized, open label study for its protective effect on skin photosensitivity. Twenty-seven patients treated with PDT for central obstructive lung cancer or esophageal cancer received either "early" or "delayed" NAC, starting 5 or 10 days after Photofrin, in a dose of 3 x 600 mg per day for 5 days. Light, obtained from a halogen lamp (fluence rate 200 mW.cm-2) was used to illuminate skin patches of 2.5 cm2 on the back (10, 25, and 50 J.cm-2). Skin response was measured by using a visual scoring system and by measuring the redness using a reflectance meter. Skin responses varied from no changes at 10 J.cm-2 to redness with edema at energies of 50 J.cm-2. In the absence of edema, measurements with the reflectance meter appeared to be more sensitive than visual scoring. In a limited number of patients, there was a trend for decreased sensitivity after NAC, but statistical analysis failed to show any significant protective effect of this short course of NAC.

Use of Arterial Blood with Glucose Reflectance Meters in an Intensive Care Unit

Use of Arterial Blood with Glucose Reflectance Meters in an Intensive Care Unit

Data Management Programs for Bedside Glucose Testing

Point-of-care testing programs are proliferating in hospitals because they can positively impact patient outcome. This point is best illustrated by nonlaboratory personnel performing glucose testing on nursing stations by using reflectance meters. To assist in the management of quality control and quality assurance data generated by such a program, four manufacturers offer data management options with six glucose meters. System features vary, but they all generally organize the data required by regulatory organizations. Future systems may include glucose testing among the battery of tests to be performed at the patient's bedside. Information gathered at the bedside could be transmitted to a laboratory information system via an infrared signal with software capable of managing this data. This is the first article of a two-part continuing education series on bedside testing. The second article will focus on hematology systems, and will be accompanied by the exam for CMLE credit in the January 1995 issue.

Effect of alcohol swabbing on capillary blood glucose measurements

AbstractA study was conducted to determine the effects of alcohol swabbing on reagent strip blood glucose (BG) measurements using Reflolux and Glucometer GX meters and the Exac Tech Pen. Sixty subjects were randomly allocated to one of the three meters. Each had three separate fingerpricks after either swabbing with 70% isopropyl alcohol and testing immediately or after drying for two minutes; or after no preparation; (n=180). BG was also determined at alcohol concentrations of 0%, 1%, 5%, 10% and 20% on hypo (1.2 mmol/l), normo (4.0 mmol/l) and hyperglycaemic (>28 mmol/) blood in vitro (six strips/meter/concentration, n=270).Increasing concentrations of alcohol caused reduction of BG at all glycaemias using the two meters (p=<0.01) (ANOVA). At alcohol concentrations of 20% the pen showed an increase of 1.5 mmol/l at euglycaemia, and an increase of 2.7 mmol/l into the normal range at hypoglycaemia (<2 mmol). Alcohol concentrations of blood in vitro caused inaccuracies in reagent strip BG readings. The errors varied with the type of meter, decreasing with reflectance meters, and increasing with the pen. In practice, however, swabbing with alcohol prior to testing had no effect on meter accuracy in the clinical setting.

Use of arterial blood with bedside glucose reflectance meters in an intensive care unit

To compare blood glucose values obtained from two different sampling sites (arterial catheter and capillary from finger puncture), which were analyzed by a bedside reflectance meter. A sample was also analyzed by standard methods (oxygen electrode oxidation in the laboratory). Prospective, cross-sectional clinical study. Cardiovascular intensive care unit (ICU) designed for postoperative open-heart surgery patients in a 1,100-bed medical center. Sequential sample of 50 patients immediately after open-heart surgery. The blood glucose concentration of each patient was analyzed on the patient's arrival to the ICU (immediately postoperatively) by three methods: one blood specimen was obtained from an arterial catheter, divided and analyzed either at the bedside by a reflectance meter (glucose method 1) or in the hospital laboratory (glucose method 2); another sample was obtained by lancing the fingertip and the glucose concentration was analyzed at the bedside in the same reflectance meter (glucose method 3). Using paired analyses to compare the mean glucose values of the bedside arterial whole blood sample (method 1) with the arterial serum sample (method 2) demonstrated that the glucose concentration in the arterial whole blood sample (method 1) was significantly (p < .001) higher. For 46 of 50 comparisons, the glucose value in the arterial whole blood sample (method 1) was higher, with a mean difference of 30 mg/dL (1.7 mmol/L). Although the mean difference was reduced to 10 mg/dL (0.6 mmol/L) when the arterial whole blood sample (method 1) was corrected for the hematocrit (i.e., < 35% [< 0.35]), the mean glucose concentration in the arterial whole blood samples (method 1) remained statistically higher (p < .05). The glucose concentration in the arterial serum sample (method 2) was significantly higher than the value determined from the bedside capillary sample (method 3) before (p < .05) and after (p < .001) correction for hematocrit. The difference in mean glucose concentrations between the arterial serum sample (method 2) and bedside capillary sample (method 3) was 9 mg/dL (0.5 mmol/L) when the capillary specimen (method 3) was not corrected for hematocrit. This difference increased to 21 mg/dL (1.2 mmol/L) when low hematocrit values were considered and appropriate adjustments of the glucose values were made. At the bedside, one can accurately correct arterial whole blood glucose values to correspond to laboratory values by the following formula: (0.94 x arterial whole blood glucose) + (4.6 x hematocrit) + (-16.5 x [37 degrees C--patient's temperature])--132 = laboratory glucose value. Since arterial whole blood samples give higher glucose results than arterial serum, the use of arterial whole blood in combination with reflectance meters must be recommended with caution. This caution is especially advised if the glucose values obtained with arterial whole blood are used in conjunction with a sliding scale of insulin, which depends on threshold concentrations of glucose. In our hospital, use of arterial whole blood in combination with reflectance meters could have resulted in an incorrect dose of insulin in 31 of 50 patients.

Effect of actual glycaemia on pupillary function in children with type 1 diabetes

The objective was to study the effect of actual glycaemia on autonomic function. Autonomic function was assessed by computerised infrared video-pupillometry in 10 children with type 1 diabetes (age 10.5–15.8, median 13.7 years, diabetes duration 1.1–10.0, median 3.8 years) on 6 occasions (07:30, 12:00, 17:30 h on days 1 and 10, respectively). Blood glucose was measured by a reflectance meter immediately prior to each pupillometry study. To allow for interindividual differences in pupillary variables (resting pupil diameter (RPD), reflex amplitude (RA), maximum constriction velocity (MCV)) the variation of each variable from the mean for the individual (difference between the actual value and the mean value from the 6 measurements (delta RPD, delta RA, delta MCV)) was used in calculations. None of the three pupillary variables showed a significant correlation with the blood glucose value (delta RPD: r = 0.072, P = 0.59; delta RA: r = −0.008, P = 0.96; delta MCV: r = −0.080, P = 0.55). It is concluded, that autonomic function in children with Type 1 diabetes as determined by computerised infrared video-pupillometry is not affected by actual glycaemia.

Intensified versus conventional management of gestational diabetes

OBJECTIVE: We tested the hypothesis that intensified management of gestational diabetes mellitus on the basis of stringent glycemic control, verified glucose data, and adherence to an established criterion for insulin initiation results in near normoglycemia control and reduction of adverse outcomes. STUDY DESIGN: A prospective, population-based study compared the effect on perinatal outcome of conventional (n = 1316) and intensified (n = 1145) management. Group assignment was based on availability of memory-based reflectance meters at entry to the program. A contemporaneous randomized control group (nondiabetic, n = 4922) was selected. RESULTS: The diabetic groups were comparable in demographic characteristics and in factors associated with higher risk for adverse pregnancy outcome, such as previous macrosomia, previous gestational diabetes mellitus, and family history of diabetes. The control group was younger, less obese, and had a lower rate of previous macrosomia. The intensified management group had rates of macrosomia, cesarean section, metabolic complications, shoulder dystocia, stillbirth, neonatal intensive care unit days, and respiratory complications lower than those in the conventional management group and comparable to those of the nondiabetic controls. Other maternal complication rates, such as for preeclampsia, chronic hypertension, and infection, were similar for the three groups. Mean blood glucose levels were a good predictor of perinatal outcome. Gestational age at delivery, previous history of macrosomia, and overall mean blood glucose levels were the only significant predictors of birth weight percentile in both diabetic groups (logistic regression). CONCLUSION: The intensified management approach is significantly associated with enhanced perinatal outcome. This management strategy clarifies the relationship between glycemic control and neonatal outcome. (SM J OBSTET GYNECOL 1994; 170:1036-47.)

Cotside plasma rather than whole blood estimates of blood glucose in the newborn.

An evaluation of the use of a glucose reflectance meter for the cotside measurement of plasma rather than whole blood glucose was undertaken. Three hundred and twelve samples were obtained for examination. There is a closer correlation between plasma glucose than whole blood glucose to laboratory values. Confidence and prediction intervals show that even separating plasma from whole blood at the cotside does not improve the reliability of glucose reflectance meters when predicting blood glucose values in the context of managing high risk newborn infants. The cotside measurement of blood glucose using glucose reflectance meters should be abandoned and improved methods for quickly obtaining accurate laboratory data should be instituted.

Potato tuber stem-end fry color determination

Precise measurement of tuber stem-end fry color is necessary to determine the fry quality of potatoes (Solanum tuberosum L.). Changes in fry color as influenced by small variations in measurement location, delays between slicing and frying, and delays between frying and measuring were examined. Variations in time between frying and measurement, and variations in the location of measurement contributed more to changes in observed color than delays between slicing and frying. The standard visual method for determining stem-end fry color was compared to objective methods using a Photovolt reflectance meter. Photovolt reflectance readings of two types of transverse stem-end tuber slices were compared with those from longitudinal strips. All methods produced closely related re-sults. Optimum sample size and applications for each method are discussed.

Cut-off values of laboratory measurements of capillary blood glucose in a glucose challenge test. Evaluation of 250 cases

SummaryThe aim of the present investigation was to select the most suitable threshold in a glucose challenge test using capillary glucose measured in the laboratory. Two hundred and fifty consecutive pregnant women who attended the antenatal clinic of the Department of Obstetrics and Gynecology of Ferrara University in 1991 were tested at 27.4± 2.8 weeks of pregnancy. One week later every patient had a confirmatory glucose tolerance test. Receiver operating characteristic curve analysis technique was used to select cut-off values. A glucose concentration of 8.3 mmol/l (150 mg/dl) was the best threshold in patients studied. This value is higher than that recommended for venous plasma and lower than those proposed for capillary glucose measured by reflectance meters.

Self-monitoring of blood glucose and insulin dose alteration in type 1 diabetes mellitus

The purpose of this study was to evaluate the relationship between proper use of self-monitoring of blood glucose (SMGB) including knowledge and application of specific algorithms and metabolic control in a group of randomly selected insulin-dependent diabetic patients. We studied 80 patients responding to the following criteria: intensive conventional insulin therapy and SMBG for at least 6 months using a reflectance meter, and previous 5-day hospital education period. The practical knowledge of the guidelines was evaluated by a questionnaire simulating 8 metabolic situations. A computer analysis of the SMBG data for the 3 months preceding the study allowed us to evaluate patient compliance with SMBG (number of blood glucose determinations) and patients' application of the guidelines (percentage of insulin doses modified according to the guidelines). Fifty-nine patients (79%) were compliant with SMBG and had better metabolic control than the non-compliers (HbA 1c: 6.7 ± 1.1% vs. 7.5 ± 1.9, P < 0.05). Twenty-eight out of the 59 compliant subjects had good knowledge of the guidelines but without patent improvement of glycemic control. Seventeen of these 28 correctly used the algorithms to modify insulin dosage; their HbA 1c levels were lower than those of the 11 patients who did not use the algorithms (6.1 ± 0.9 vs. 7.1 ± 0.9%, P < 0.05). The percentage of insulin dose modification consistent with the guidelines and the level of HbA 1c was negatively correlated in the good-knowledge group. The conclusion is that good metabolic control is linked not only with the degree of knowledge but also with the application of this knowledge.

Assessment of skin erythema by eye, laser Doppler flowmeter, spectroradiometer, two-channel erythema meter and Minolta chroma meter.

Visual grading, a laser Doppler flowmeter, a spectroradiometer, a two-channel erythema meter and a Minolta chroma meter were compared in the measurement of erythemas arising from immediate contact reactions produced either by 250 mM benzoic acid or 10 mM methyl nicotinate in petrolatum in an open application test or by ultraviolet irradiation. A good correlation between visual grading and objectively measured values was found for all the instruments, but the laser Doppler flowmeter gave proportionally lower values for the ultraviolet erythemas than the skin reflectance meters, suggesting that these differ from erythemas induced by benzoic acid or methyl nicotinate. The laser Doppler flowmeter gave less repeatable results than other meters when measuring moderate and pronounced erythemas produced by ultraviolet irradiation. Measuring both the blood flow and the actual erythema may give more information about the reaction than either measurement system alone.

Instruments for Measuring Subice Algal Profiles and Productivity in situ

Instruments have been developed for the in situ measurement of concentration and productivity of bottom ice algal layers in Resolute Passage, eastern Canadian Arctic. Measurements are accomplished by deploying an instrument on an arm articulated remotely through a hole in the ice, sampling the subice surface, and finally recovering the instrument and sample. The first instrument is an incubation system that is used to measure in situ productivity of a subice core. Results show the extent and range of productivity in bottom ice, with low and high biomass at the commencement of the algal bloom and near the end of the bloom period, respectively. The second instrument is a reflectance meter that can be used to measure chlorophyll profiles at the subice surface. The meter was calibrated against measured chlorophyll concentrations of extracted cores. After calibration the instrument can be used to measure integrated chlorophyll (milligrams per square metre) and profiles (milligrams per cubic metre) rapidly and synoptically. Deployment of the arm coupled with a plankton pump sampler is also briefly described.

Two-channel fiber optic skin erythema meter

The skin erythema meter is a fiber optic, dual-wavelength reflectance meter that measures the reflectance of the skin on two wavelengths, one the blood/hemoglobin absorption band (555 nm) and another a reference (660 nm). The instrument consists of a fiber optic sensor head, a microprocessor-based control and analysis unit, and a plotter, and it presents the relation between the measured reflectance results in terms of a reflectance index [R(555 nm):R(660 nm)]. The measurement cycle, including printing, takes 5 s. Stability tests on the erythema meter (constant distance, reference object) showed the standard deviation of the reflectance index to be ± 0.1%, whereas that in repeatability tests was less than ± 0.5% for skin and less than ± 0.2% for paper with handheld positioning and repetition. The dynamic change in the reflectance index was about 30% with strong irritation. Results of various irritation test series on human skin are also presented. Finally, the performance and applicability of the skin erythema meter with respect to allergy test procedures, irritancy testing, and measurement of uv-induced erythema are discussed.

Fetal surveillance in pregnancies complicated by insulin-dependent diabetes mellitus

Our objective was to determine whether maternal vascular disease and/or glycemic control can be related to tests of fetal condition in diabetic pregnancies. A total of 114 women with insulin-dependent diabetes who used a memory-based glucose reflectance meter were prospectively evaluated. Nonstress testing was begun weekly at 28 to 30 weeks and twice weekly at 32 weeks. A nonreactive nonstress test was followed by a biophysical profile in all cases. A total of 1676 nonstress tests was performed (14.7 +/- 3.2 tests per patient). Eight percent (n = 134) were nonreactive, necessitating a biophysical profile. A comparison of ambulatory glucose profile data, including mean blood glucose level, variation, and excursions from the median, revealed no significant differences in patients with reactive versus nonreactive nonstress tests. Ten patients, including eight with vascular disease, were delivered because of abnormal test results of fetal condition. Nephropathy or hypertension was associated with intervention for fetal well-being in 8 of 20 women (40%) with these risk factors. Only 2 of 94 patients (2%) without nephropathy or hypertension required delivery because of abnormal results of fetal testing (p less than 0.001). One fetal death occurred. No significant differences in the various glycemic parameters were found in women delivered for suspected fetal jeopardy versus the nonintervention group. Pregnancies complicated by vascular disease are at greatest risk for abnormal results of fetal testing that necessitate early delivery. Women without vascular complications and with maintenance of good glycemic control rarely have fetal compromise.

Use of blood glucose data by families of children and adolescents with IDDM.

Prospective evaluation of the use of blood glucose test results for treatment actions by families of youth with IDDM. Forty-seven patients with IDDM used reflectance meters with memory for SMBG for 28 days. Parents kept weekly diaries of six types of uses of SMBG data. We collected SMBG data from the reflectance meters, HbA1 and serum fructosamine assays, and measures of behavioral factors that could affect use of SMBG data. Families recorded a mean of 4.85 data-based actions during the 28-day study, and 74% of the families reported at least one such action. Fifty percent of recorded actions consisted of management of hypoglycemia and, among the remainder, only 18% were anticipatory, proactive actions. Partial correlation analysis showed that families with more frequent use of SMBG data had less parent-child conflict about diabetes, more diabetes knowledge, and better overall treatment adherence. Use of SMBG data was unrelated to objective indices of the need for treatment adjustments or to diabetic control. Most families made active use of their SMBG data, but few of these actions were proactive. Behavioral factors were stronger predictors of family use of SMBG data than were objective indices of the need for treatment adjustments. The results illustrate the need for further research on use of SMBG data and methods to enhance its impact on diabetic control.

Reliability of glucose measurement by glucose test strips in tropical conditions

The reliability of glucose test strips and reflectance meters after storage in tropical conditions was assessed. In a first experiment, sealed bottles containing glucose test strips were stored for 1 month in closed sterilising ovens at 40°C, one in dry (0% humidity) and the other in wet (75% humidity) conditions. Results were compared to measurements obtained with glucose test strips stored under standard Western conditions, in non-diabetic and diabetic patients, using the same standard reflectance meter. A second experiment was performed similarly, comparing the values obtained with reflectance meters stored in different conditions, using standard glucose test strips. Reproducibility was assessed on the basis of duplicate measurements for each condition of storage. We observed that temperature and humidity did not significantly affect the glucose test strips (1st experiment), while a slight underestimation of capillary blood glucose was found using reflectance meters stored at 50°C, irrespective of the humidity (2nd experiment). All the correlation coefficients between duplicates were > 0.975 irrespective of the conditions of storage for glucose test strips and reflectance meters. Therefore, glucose test strips and reflectance meters appear fairly reliable at the grass-root level in the tropics, if used carefully.