Reflectance Photometer Research Articles

A Method for Compensating Hemoglobin Interference in Total Serum Bilirubin Measurement Using a Simple Two-Wavelength Reflectance Photometer.

Neonatal hyperbilirubinemia (NH) is a common condition in newborns, with elevated bilirubin levels potentially causing neurological damage or death. Accurate and timely measurements of total serum bilirubin are essential to prevent these outcomes. Direct spectrophotometry, a reliable method for measuring bilirubin, is particularly useful in constrained settings due to its potential for portable low-cost instrumentation. However, this method is susceptible to interference from hemoglobin, often present due to hemolysis. Typically, this interference is reduced using complex optical filters, reagents, multiple wavelengths, or combinations thereof, which increase costs and complexity while reducing usability. This study presents a hemoglobin compensation algorithm applied to a simple, portable, two-wavelength (465 and 590 nm) reflectance photometer designed to receive 30 µL of plasma or whole blood samples and perform the measurement without any reagents. Testing across five bilirubin and hemoglobin levels (4.96 to 28 mg/dL and 0.06 to 0.99 g/dL, respectively) demonstrated that the algorithm effectively reduces hemoglobin interference and overestimation errors. The overall root mean square error was reduced from 4.86 to 1.45 mg/dL, while the measurement bias decreased from -4.46 to -0.10 mg/dL. This substantial reduction in overestimation errors supports future clinical trials with neonatal blood samples.

Newborn Skin Maturity Medical Device Validation for Gestational Age Prediction: Clinical Trial.

BackgroundEarly access to antenatal care and high-cost technologies for pregnancy dating challenge early neonatal risk assessment at birth in resource-constrained settings. To overcome the absence or inaccuracy of postnatal gestational age (GA), we developed a new medical device to assess GA based on the photobiological properties of newborns’ skin and predictive models.ObjectiveThis study aims to validate a device that uses the photobiological model of skin maturity adjusted to the clinical data to detect GA and establish its accuracy in discriminating preterm newborns.MethodsA multicenter, single-blinded, and single-arm intention-to-diagnosis clinical trial evaluated the accuracy of a novel device for the detection of GA and preterm newborns. The first-trimester ultrasound, a second comparator ultrasound, and data regarding the last menstrual period (LMP) from antenatal reports were used as references for GA at birth. The new test for validation was performed using a portable multiband reflectance photometer device that assessed the skin maturity of newborns and used machine learning models to predict GA, adjusted for birth weight and antenatal corticosteroid therapy exposure.ResultsThe study group comprised 702 pregnant women who gave birth to 781 newborns, of which 366 (46.9%) were preterm newborns. As the primary outcome, the GA as predicted by the new test was in line with the reference GA that was calculated by using the intraclass correlation coefficient (0.969, 95% CI 0.964-0.973). The paired difference between predicted and reference GAs was −1.34 days, with Bland-Altman limits of −21.2 to 18.4 days. As a secondary outcome, the new test achieved 66.6% (95% CI 62.9%-70.1%) agreement with the reference GA within an error of 1 week. This agreement was similar to that of comparator-LMP-GAs (64.1%, 95% CI 60.7%-67.5%). The discrimination between preterm and term newborns via the device had a similar area under the receiver operating characteristic curve (0.970, 95% CI 0.959-0.981) compared with that for comparator-LMP-GAs (0.957, 95% CI 0.941-0.974). In newborns with absent or unreliable LMPs (n=451), the intent-to-discriminate analysis showed correct preterm versus term classifications with the new test, which achieved an accuracy of 89.6% (95% CI 86.4%-92.2%), while the accuracy for comparator-LMP-GA was 69.6% (95% CI 65.3%-73.7%).ConclusionsThe assessment of newborn’s skin maturity (adjusted by learning models) promises accurate pregnancy dating at birth, even without the antenatal ultrasound reference. Thus, the novel device could add value to the set of clinical parameters that direct the delivery of neonatal care in birth scenarios where GA is unknown or unreliable.International Registered Report Identifier (IRRID)RR2-10.1136/bmjopen-2018-027442

Diabetes screening and the distribution of blood glucose levels in rural areas of North India.

Background and Objectives:Genetics and environment have both been implicated in the exponential rise in the prevalence of diabetes mellitus that affects 65.1 million people, and leads to a mortality of 1 million people every year in India. This study was devised to obtain the trends of the distribution of blood glucose, and sociodemographic characteristics in rural areas of a North Indian state.Materials and Methods:A cross-sectional study was conducted at eight centers in five districts. A camp-based approach was followed in the diabetes screening conducted in rural areas. Blood glucose measurements were obtained after informed consent by trained staff using a reflectance photometer instrument. Descriptive statistics, distribution curves, log transformations, and tests for bimodality were obtained.Results:45,318 participants consisting of 44.4% males and 55.6% females were screened. Ages ranged from 18 to 98 years with the mean age of 39.9 ± 14.44 years. 86.5% were normal (random blood sugar [RBS] <140 mg/dl), 10.6% were prediabetic (RBS 140–200 mg/dl) and 2.9% were diabetic (RBS > 200 mg/dl). The median blood glucose level steadily rose with increasing age. The prediabetic to diabetic ratio was 4:1. The distribution curve of RBS was right skewed. A log transformation was applied, and bimodality was tested using the Hartigan's dip test. The dip statistic (D) was 0.0162 with a simulated P < 0.001.Conclusion:Mass screening for diabetes provides benefits from a clinical standpoint by helping to estimate the prevalence (diabetes) and the hidden burden of the disease (prediabetes). Screening programs can strengthen healthcare system initiatives and reduce the growing burden of diabetes in India.

UrineCART, a machine learning method for establishment of review rules based on UF-1000i flow cytometry and dipstick or reflectance photometer

Automated systems have been broadly used in the counting of particles in urine, while manual microscopic analyses are still required for confirming components of urine sediments, especially pathologic casts and other unknown particles. Good review rules can reduce the number of manual urine microscopy examinations safely, thereby increasing productivity. Although several methods have been proposed,establishment of microscopic review rules for fl ow cytometer remains challenging. A total of 3014 urine samples from outpatient and inpatient were examined using UF-1000i flow cytometry,Urisys-2400 dipstick and RS 2003 urine sediment workstation,respectively. Based on the results above, three supervised machine learning methods were employed to construct classifiers for screening urine samples. Here, we propose a novel method for construction of microscopic review rules, termed UrineCART, which was based on a classification and regression tree (CART) method.With a cut-off value of 0.0745 for Urine CART, we obtained a sensitivity of 92.0 % , a specificity of 81.5 % and a total review rate of 32.4 % on an independent test set. Comparisons with the existing methods showed that Urine CART gave the acceptable sensitivity and lower total review rate. An algorithm based on machine learning methods for review criteria can be achieved via systematic comparison of UF-1000i flow cytometry and microscopy.Using Urine CART, our microscopic review rate can be reduced to around 30 % , while decreasing significant losses in urinalysis.

Performance Characteristics of Dipstick and Microscopic Urinalysis for Diagnosis of Urinary Tract Infection

Aim: Although the urine culture is used as the reference standard to determine presence or absence of urinary tract infection, the culture is an expensive and time-consuming method. The objectives of the study were to compare dipstick urinalysis with microscopic urinalysis and to compare dipstick and microscopic urinalysis results with urine culture results, by calculating performance characteristics of these tests. Method: The 250 morning urine specimens were performed by using dipstick and microscopic urinalysis and cultured. Laboratory urinalysis included semi-automated dipstick reading by a Miditron-M Reflectance photometer and microscopic examination. Result: Thirty-five point six percent (89/250) of patients had urine cultures with 105 colonies/mL or greater. Sensitivity and specificity of microscopic urinalysis were 91% and 68%, whereas in dipstick urinalysis they were 80% and 60%, respectively. Negative predictive values were 84% for urine dipsticks and 93% for microscopic urinalysis. Positive predictive values were 52% and 61% for dipstick and microscopic urinalysis, respectively. Conclusion: The study has suggested that both urinalysis methods can be used for rapid diagnosis. Urine culture is an expensive test for routine use and should not be applied unless the result of the nitrite, leukocyte or bloods are positive in dipstick or leukocyte, erythrocyte or bacteria are positive in microscopic examination.

Research of reflectance photometer based on optical absorption

Gold-labeled lateral flow (LF) assay has been studied extensively due to its sensitiveness, simpleness, and rapidness. In this paper, scattering properties of nanogold particles and LF strip were analyzed. Based on the above analysis, a reflectance photometer has been developed for LF strip labeled by nanogold particles. The integration of reflection optical density was used to indicate the signal of T line and C line. A quantitative equation for cardiac troponin I (cTnI) was deduced to realize quantification of the real cTnI sample, whose correlation of coefficient ( R 2) was 0.989. The variation coefficient (CV) of repetitive experiments was less than 5%. The reflectance photometer was simple, sensitive, stable, and suitable for field detection.

Theoretical model and quantif ication of reflectance photometer

The surface morphology of lateral flow (LF) strip is examined by scanning electron microscope (SEM) and the diffuse reflection of porous strip with or without nanogold particles is investigated. Based on the scattering and absorption of nanogold particles, a reflectance photometer is developed for quantification of LF strip with nanogold particles as reporter. The integration of reflection optical density is to indicate the signals of test line and control line. As an example, serial dilutions of microalbunminuria (MAU) solution are used to calibrate the performance of the reflectance photometer. The dose response curve is fitted with a four-parameter logistic mathematical model for the determination of an unknown MAU concentration. The response curve spans a dynamic range of 5 to 200 µg/ml. The developed reflectance photometer can realize simple and quantitative detection of analyte on nanogold-labeled LF strip.

Reflectance spectrophotometry in the objective assessment of dye laser-treated port-wine stains.

At present, the treatment of choice for congenital capillary malformations of the port-wine stain type (PWS) is the flashlamp pulsed dye laser. Good results can be obtained in the majority of patients with this technique, but there is a group of poor responders. In the search for predictive tools to determine the therapeutic outcome, we have used a new photoelectric reflectance instrument. Sixty-six patients with PWS, mainly on the face, were treated with a pulsed dye laser during a 21-month period. Using a hand-held reflectance photometer, erythema indices were obtained for the PWS and normal skin. Based on these indices, a relative blanching effect could be calculated. The therapeutic result was judged to be excellent in 19, good in 20, fair in 14 and poor in 13 patients. There was a good correlation (r = 0.844) between the degree of blanching and the therapeutic result. In the 'excellent' category, an average blanching effect of 47% was present after the first treatment, and this increased to between 75 and 100% after successive treatments. In the 'poor' category, the blanching effect after one treatment averaged 14%, increasing to only 40% after up to six treatments. It thus seems to be possible to predict the outcome of therapy, which is of considerable help in treatment planning. Reflectance measurements, an objective estimate of blanching, correlate well with the clinical results, and are helpful in monitoring and predicting the therapeutic outcome in dye laser-treated PWS.

Screening for Significant Bacteriuria in Patients with Upper Tract Calculi Using Dipstick Urine Analysis

Screening for Significant Bacteriuria in Patients with Upper Tract Calculi Using Dipstick Urine Analysis

Clinical utility of a rapid test for uristatin

Objectives: Uristatin is a trypsin inhibitor present in urine that is increased in most patients with bacterial or viral infections and in many with inflammatory disorders. We included the assay of uristatin as part of a screening program carried out by pediatricians on 4207 Japanese schoolchildren to judge the ability of uristatin to identify those with an infection and (or) inflammation of any cause. We used urine dipsticks for the assay of uristatin, creatinine, albumin, blood, leukocyte esterase, and protein. We also performed quantitative assays for uristatin and creatinine. Another aim was to estimate the reference range for uristatin in schoolchildren, ages 5 to 14 yr. Methods: We prepared dipstick pads that were impregnated with a chromogenic substrate for trypsin and measured the uristatin-caused inhibition of trypsin in urine. We measured creatinine so that the ratio of uristatin to creatinine could be calculated to correct for urine concentration. Results: We obtained quantitative uristatin and creatinine results for 4207 children. Of these, 177 had an abnormal urine dipstick for albumin or blood or protein or leukocyte esterase or a combination of these. We used data from 3622 children to establish the reference range for the uristatin dipsticks. The 3622 were diagnosed by their pediatricians as free from an infection or inflammation of any cause and with normal urine dipstick tests. We recommend an upper reference limit for uristatin by dipstick of ≤7.5 mg uristatin/g creatinine. The leftover 408 children ( [4207–3622-177] = 408) fell into two groups: 205 with diagnoses of no infection, possible infection, or possible inflammatory disorders. The remaining 203 children were renal disease follow-up cases. The diagnoses were based on a physical examination, microscopic urinalysis plus urine dipstick tests for albumin, blood, creatinine, protein, leukocyte esterase and a complete blood count. In the 205 children, 46 had an abnormal uristatin dipstick test, 39 had an abnormal uristatin by immunoassay, 41 had an abnormal erythrocyte sedimentation rate (ESR), 27 had an abnormal serum C-reactive protein (CRP), and one had an abnormal urine microscopic exam. For the first 938 children in the study, the agreement was 93% of negative dipstick uristatin results and immunoassays. The agreement of positive uristatin dipsticks with immunoassays was 85%. We assumed that the immunoassay results were correct. In the evaluation of 189 children with fever, 62 also had an abnormal uristatin by dipstick. Discussion: A rapid dipstick test for uristatin read on a reflectance photometer gave values that compared well with a quantitative immunoassay method. The uristatin test is sensitive but not specific for any cause of infection or inflammation. Uristatin is easy to determine and appears to be a better indicator than fever, ESR, or CRP for the diagnosis of an infection or inflammation.

GIT (Glucose Infusion Test): Polycentric Evaluation of a New Test for Vascular Access Recirculation

Introduction. Vascular access recirculation (AR), which is often unacknowledged, remains an important cause of inadequate dialytic dose. The glucose infusion test (GIT) is a new method for detecting and quantifying AR. This paper reports on a polycentric evaluation of the new test and a comparison with the classical Urea-test (UT). Methods. GIT protocol comprises withdrawal from the arterial port (sample A), injection into the venous drip chamber of 1 g glucose in 4 seconds, withdrawal from the arterial port (sample B) continuously from 13 to 17 seconds. Glucose is determined on A and B by a reflectance photometer. If B = A then there is no recirculation. If B exceeds A by at least 20 mg/dl there is recirculation. AR quantification: AR% = (B-A) / 20. GIT was performed on 623 patients from eleven dialysis centers to screen the patients for AR. Subsequently, GIT and Urea-test (UT) were compared in 189 paired tests. The reproducibility of GIT and UT was studied in 28 paired tests performed in sequence. Results. The screening test by GIT was positive in 68 cases (11 %). The majority of positivities was found in central venous catheters (CVC, 27/50 cases, 54 %), whereas only 7 % of artero-venous fistulas (AVF) were positive. In the CVC group, Tesio catheters were more frequently positive compared to Dual Lumen Catheters (64 % vs. 29 %). The comparison GIT - UT showed that results matched in 162 tests (79 negative and 83 positive both by GIT and UT), showing that on the grounds of UT, GIT has high sensitivity and specificity. In 27 tests GIT was positive, but UT negative. This disagreement is due to the different minimal limit of detection, 1 % for GIT and 5% for UT. The reproducibility was greater with GIT than with UT with a lower D% (respectively -0.6 +/- 2.5 and -0.4 +/- 6.1 %, p<0.001) and a lower coefficient of variation (17 vs 33 %). Conclusions. The screening of 623 patients by GIT confirmed that AR in AVF is normally absent, whereas an un-expectedly high frequency of moderate AR in CVC was found. The GIT-UT comparison showed that the new test is simple and immediate, and gives results with higher accuracy, sensitivity and reproducibility than UT.

Glucose infusion test: A new screening test for vascular access recirculation

Vascular access recirculation is an important cause of diminished dialysis efficiency. We propose a new screening test based on glucose infusion as a tracer for recirculation. The glucose infusion test (GIT) protocol comprises a basal blood sample (A) from the arterial port, a 5 mL bolus of 20% glucose into the venous chamber (time 0), followed by a second sample (B) in four seconds (from 13 to 17 s with QB 300 mL/min) from the same port. The blood glucose level is determined at the bedside on A and B with a reflectance photometer (CV 1.8%). Interpretation of the test is straightforward: If B = A, there is no recirculation, whereas if B > A, recirculation can be calculated from the regression equation: 0.046 x (B - A) + 0.07, obtained from in vitro tests reproducing artificial recirculation at 0, 5, and 10%. To validate this new method in vivo, we compared GIT and the urea test on 39 hemodialysis patients, obtaining a good correlation (r = 0.93). The two tests were considered positive (recirculation present) when the lower 95% confidence intervals were more than zero. Our patients were divided into two groups: those with (22 out of 39, mean recirculation 11.8%) or without recirculation (17 out of 39, mean 0.06%). The urea test did not recognize 7 out of 22 patients because they had a small recirculation below the urea test limit of detection. GIT was more sensitive (detection limit 0.3%), simpler, and immediate in showing the results than the urea test. It is an accurate and low-cost technique for screening and follow-up of vascular access in a dialysis unit.

Comparative performance of three test methods for determining chipping quality in tubers of potato (Solanum tuberosum L.)

The capacity of a colour chart and a reflectance photometer (Agtron) to accurately determine chipping quality of potato tubers was assessed using data sets taken over a 4-yr period for 17–32 cultivars. Both tests gave a high diagnostic accuracy for chipping quality regardless of sampling time from storage or the occurrence of high temperature reconditioning when evaluated by receiver operating characteristic (ROC) curve analysis. Receiver operating characteristic curve analysis showed that both tuber glucose content and chip colour provided good diagnostic performance in correctly separating processing from non-processing tubers over a range of growing and storage conditions. Identification of chipping from non-chipping tuber samples from a 13 °C storage across a range of cultivars and growing conditions occurred with a minimum chipping colour threshold range of 41–47 or a maximum glucose concentration range of 4.3–5.4 mmol L−1 of tuber cell sap. The practical value of a test can depend on such factors as prevalence of chippers in a tuber population as well as the cost of misclassifications, i.e., costs associated with false positive or false negative test results and expressed in relative terms as the unit cost ratio. An examination of Prevalence-Value-Accuracy (PVA) plots for one of the data sets indicated that total misclassification costs could increase rapidly, depending on the prevalence of chipping tubers and the relative amounts of false negative and false positive costs. Maximum costs were consistently associated with a prevalence of 50% chippers and a unit cost ratio of 0.5. In a tuber sample containing a high prevalence of chippers (50–70%) and a low unit cost ratio (&lt;0.2), an acceptable colour threshold determined by PVA-Threshold (PVAT) plots would be approximately 40 to 50 from the Agriculture and Agri-Food Canada colour chart. However, if the colour chart was used for screening tuber samples with a low prevalence (20–40%) of chippers and a unit cost ratio &gt;0.20, a threshold between 60 and 65 would be optimum. The latter range would be conservative and agrees with, and supports, current industry standards, which reside at 60 or better. Since a good diagnostic test should be repeatable and subject to minimal inter-observer variation, the more objective glucose or reflectance photometric tests may be preferable and provide acceptable diagnostic accuracy for processing quality. However, the present study indicates that all three test methods are acceptable for accurately separating chipping from non-chipping tubers regardless of sampling or storage protocols. Key words: Potato, colour chart, reflectance colorimetry, glucose content

Evaluation of a New Portable System for Cord Lactate Determination

To evaluate a new reflectance photometer (Accusport^®) for blood lactate determination, a prospective non-interventional study was performed on blood obtained from the umbilical cord artery immediately after delivery of the baby in 109 consecutive women. For each sample, the results of cord arterial blood lactate values measured with the reflectance photometer were compared with those obtained using a reference method in the laboratory. The values obtained using Accusport were comparable in accuracy with those obtained using a laboratory reference method (Ektachem 9501RC). The instrument provides a simple and reliable method for determining cord arterial blood lactate levels in a small blood sample.

Comparison of two reflectance photometers in the assessment of neonatal hypoglycaemia.

To assess the accuracy and reliability of reflectance photometers in estimating blood glucose concentrations, two were assessed: the Ames Glucometer 3 (Bayer Diagnostics) with Glucofilm Test strips; and the Reflolux S (Boehringer Mannheim) with BM Test Glycemia 20-800 strips. These were compared with laboratory blood glucose estimations in 100 assays (50 comparisons for each machine, measuring the difference (d) between the glucose reading and the mean of the reflectance photometer and the laboratory value). The Ames Glucometer 3 (mean d = + 0.7 mmol/l, (SD 1.1) mmol/l) was less accurate than the Boehringer Reflolux S (mean d = 0.2 mmol/l, (SD (0.7) mmol/l). The range of error of both machines is wide (Ames 2 SD range + 2.9 mmol/l to -1.5 mmol/l true readings; Boehringer + 1.8 mmol/l to -1.2 mmol/l of true readings). Because of this, any reflectance photometer readings that are even slightly low should be checked with laboratory estimations. The clinical value of such machines is limited in infants with low blood glucose concentrations.

Screening for Gestational Diabetes Mellitus With a Reflectance Photometer

To investigate the accuracy and precision of a recent-generation reflectance photometer, Accu-Chek III, for gestational diabetes mellitus screening with a single operator. Four hundred ten paired capillary and serum glucose samples collected prospectively were evaluated by a reflectance photometer and a glucose oxidase method (Beckman), respectively, during routine gestational diabetes mellitus screening with a single operator. The mean Accu-Chek III result was 12% greater than serum glucose oxidase (115.5 +/- 1.4 and 103.4 +/- 1.3 mg/dL, respectively). A serum glucose level of at least 135 mg/dL by glucose oxidase produced sensitivity and specificity of 0.81 and 0.68, respectively. At 155 mg/dL, the Accu-Chek III sensitivity was 0.81 and specificity 0.74, and the method produced fewer false-positive results (37 of 410 [9.0%] versus 41 of 410 [10%]) than a 135-mg/dL serum cutoff. Adjusting the Accu-Chek III threshold by two times the coefficient of variation resulted in the same number of false positives as the Beckman technique at 135 mg/dL. The receiver operating characteristic curve cutoff for the venous value of 135 mg/dL was an Accu-Chek III value of 141 mg/dL. Linear regression analysis predicted y = 20.6 + 0.919x, r = 0.838. The mean coefficient of variation was 3.9%. The Accu-Chek III produced accurate and precise gestational diabetes mellitus screening results with a single operator. Because capillary blood is a combination of arterial and venous blood, an Accu-Chek III cutoff of 155 mg/dL may be more appropriate for screening, considering the 10-15% higher capillary glucose level in the fed state. An Accu-Chek III cutoff of 155 mg/dL produced a higher specificity than venous serum at 135 mg/dL, with no decrease in sensitivity.

Random Blood Glucose Values in the Last Trimester of Pregnancy

Sixty-nine Kuwaiti and 115 non-Kuwaiti Arab women with gestational ages ≧ 25 weeks were screened using a reflectance photometer to determine random capillary blood glucose (RCBG). All known diabetics

A Path Model of Type A and Type B Responses to Coping and Stress In Employed Black Women

The purpose of this study was to test a conceptual model of the effects of age, weight, type, cholesterol, systolic blood pressure, and coping on the stress response of southern black women. Data were collected on 280 employed black women. Audiotape analyses of the structured interview resulted in 136 Type A's and 144 Type B's. Each individual was screened for hypercholesteremia using a portable reflectance photometer. Blood pressure measurements were taken every minute before, during, and after a stress-producing Type A/B interview. Type A's had higher resting systolic blood pressures, higher cholesterol levels, higher levels of stress during the interview, and lower coping scores than Type B's. The relationships between age, weight, and resting systolic blood pressures all were in the direction reported in the literature.

Measurement of glucose in cerebrospinal fluid with reagent strips and a reflectance photometer

Measurement of glucose in cerebrospinal fluid with reagent strips and a reflectance photometer

A unitized enzyme-labeled immunometric digoxin assay suitable for rapid testing

An enzyme-labeled immunometric assay has been developed for measuring digoxin concentrations in serum or plasma. Unitized, compartmentalized reagents are used with an automated sample-processing instrument. The enzyme activity of the processed sample, which is directly proportional to the digoxin concentration, is measured by using a reagent strip and the Ames Seralyzer reflectance photometer. The test takes less than 15 min, and digoxin concentrations are calculated from a two-point calibration line stored in the instrument. Within-run CVs for controls at four concentrations ranged from 2.3% to 3.8%; between-run CVs were from 1.5% to 2.6%. Results obtained with clinical serum samples correlated well (r greater than 0.96) with those obtained by fluorescent polarization immunoassay (Abbott TDx) and RIA (Clinical Assays and NML). This rapid and convenient method for monitoring digoxin concentrations in serum or plasma is particularly well suited for decentralized sites such as emergency rooms, urgent-care centers, and physicians' offices.