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Sensitivity, specificity, and predictive values of reagent test strip estimations of blood urea nitrogen.

Azostix-reagent-tests(R) strips (Ames, Miles, Inc., Diagnostic Division, Elkhart, IN) were used to measure blood urea nitrogen values in blood samples from 125 dogs and cats at the North Carolina State University, College of Veterinary Medicine. Results of the tests were compared with standard serum urea nitrogen results. Sensitivity, specificity, and negative predictive values were high (86.4, 90.3, and 96.5%, respectively). Positive predictive value was low, 65.5% of the dogs and cats with elevated blood urea nitrogen values were correctly classified as abnormal The test performs well when the prevalence of abnormal values is near 50%.

Journal Article↗

Comparative evaluation of the Eiken and API 20E systems and conventional methods for identification of members of the family Enterobacteriaceae.

To evaluate the accuracy and utility of the Eiken Systek No. 1 (Eiken system; Eiken Chemical Co., Ltd., Tokyo, Japan), we conducted a clinical comparison, with 345 Enterobacteriaceae isolates, of the Eiken System with API 20E (Analytab Products, Inc., Plainview, N.Y.) and conventional methods. The Eiken system is a 21-biochemical-test battery tray stored at 25 degrees C and inoculated in one step. It is similar to the API 20E except that the Eiken system contains malonate, adonitol, and maltose; lacks gelatin, sucrose, melibiose, amygdalin, and arabinose; and uses reagent strips instead of liquid reagents. The API 20E and Eiken systems correctly identified 339 (97.7%) and 276 (79.5%), respectively, and misidentified 3 (0.9%) and 13 (3.7%), respectively, of the isolates. There were no identification codes for 5 (1.4%) organisms with the API 20E and 58 (16.7%) organisms with the Eiken system; of these latter unidentified organisms, 42 were identified as Proteus spp., Morganella sp., and Providencia rettgeri by conventional methods. There was no significant difference between the two rapid systems in total time required for inoculation and reading. Modifications for interpretation of decarboxylase and oxidase tests were needed for the Eiken system, and manipulation of reagent strips required considerable dexterity. However, the Eiken system was easier to inoculate than the API 20E, and, with minor increases in the data base to include more of the Proteus and Morganella spp. and P. rettgeri, the system should be reliable for identification of members of the family Enterobacteriaceae.

Computers↗

The reproducibility of urinalysis using multiple reagent test strips.

Ninety urine samples were examined twice by 3 "observers" (two persons, using only visual observation, and one person using a spectrophotometric analyser) using multiple reagent teststrips. To determine reproducibility, inter- and intra-observer agreement were calculated and expressed as Cohen's kappa and as weighted kappa. The results show negligible intra-observer differences between the visual and spectrophotometric observation. The lack of agreement between inter- and intra-observer urinalysis results, using multiple reagent test strips was disappointing, considering the simplicity of the test procedure. Further improvement of reproducibility, e.g. by enhancing the discoloration of the test pads, is necessary. Reproducibility is not improved by using a spectrophotometric analyser instead of visual reading of the test strips.

Esterases↗

A control system for monitoring the performance of leukocyte strip tests.

The control system described here is used to monitor the performance of urinary reagent-strip tests for leukocytes. The presence of leukocyte esterase in the urine is used as a marker for leukocytes in urine. The control system is based on sonicated leukocytes, isolated from whole blood. The esterase activity of this sonicate is determined by spectrophotometry with the N-tosyl-L-alanine ester of 5-phenyl-3-hydroxypyrrole as substrate. The assay result is used to determine the amount of sonicate needed to prepare buffered esterase-containing solutions. Such control solutions mimic leukocytic urines and are stable for 6 h at room temperature. The variability of the control system was tested by preparing it five times in a day on five separate days. The overall CV for Leukostix Reagent Strips (Ames Division, Miles Laboratories, Inc.) when tested with these solutions and analyzed with a reflectance spectrophotometer was 8%; for visual readings it was 10%. The overall CV for Chemstrip LN Reagent Strips (Biodynamics, Indianapolis, IN) was 10%.

Cell Separation↗

Comparison of home monitoring methods for feline urine pH measurement.

BACKGROUND: Monitoring of urine pH, often done in the patient s home, is essential for proper clinical treatment and management of conditions such as urolithiasis. OBJECTIVE: The purpose of this study was to assess the agreement in pH readings between a standard laboratory method and methods readily available for home monitoring. The influence of refrigerated storage on urine pH was also examined. METHODS: Urine samples were obtained by cystocentesis from 40 clinically healthy cats, and pH was measured within 2 hours of collection. Each sample was evaluated using pH paper, urinalysis reagent strip, 2 brands of portable pH meters (Chek-Mite, Corning, Corning, NY, USA; and Checker 1, Hanna Instruments, Woonsocket, RI, USA), and a standard laboratory benchtop pH meter. Urine samples were refrigerated, and a second pH reading was obtained with the laboratory benchtop meter after 24 hours. The degree of agreement was assessed among the different methods, with the laboratory benchtop pH meter as the reference method. RESULTS: The closest agreement was obtained with the Chek-Mite portable pH meter and least agreement with the Checker 1 portable pH meter, which had a constant negative bias of 0.31 units due to expiration of the electrode. As expected, pH paper and reagent strips had poor and intermediate agreement, respectively. The reagent strip method had a negative bias of 0.12 units when compared with the benchtop pH meter and wide disagreement at the low pH end. The reagent strip did not agree strongly with the reference method; only 50% of values were within 0.25 pH units of each other. The difference in pH between 0 hours (6.57 +/- 0.54) and 24 hours of refrigeration (6.61 +/- 0.53) was not considered clinically significant. CONCLUSION: Portable pH meters are excellent for monitoring urine pH at home as long as attention is given to electrode maintenance. Urine can be collected at home and kept refrigerated, and pH may be measured reliably within 24 hours using the reference method or a portable pH meter.

Animals↗

Comparison of two methods of measurement of whole blood glucose in the neonatal period.

The purpose of this study was to compare the performance and accuracy of the HemoCue B-Glucose photometer system and reagent strip tests used in conjunction with reflectance photometry against a reference plasma glucose method. One hundred consecutive babies admitted to the neonatal unit over a 6-month period were enrolled in the study. Each baby had a heelprick capillary glucose measured by HemoCue and reagent strip tests. At the same time venous plasma glucose and haematocrit were measured. The mean difference between the reagent strip test and plasma glucose was significantly less than the corresponding value for the HemoCue (0.015 +/- 1.41 vs 0.837 +/- 1.565 mmol l-1, mean +/- SD); however, the agreement limits between both methods and plasma glucose were wide. No significant effect of haematocrit was detected on either method. The HemoCue photometer does not offer any advantage over the widely used reagent strip tests in the neonatal period. However, the limits of agreement of both methods compared with plasma glucose are too wide to be clinically acceptable in the neonatal period.

Blood Glucose↗

Measurement of glucose in tracheobronchial secretions to detect aspiration of enteral feedings.

OBJECTIVES: To determine (1) the relationship between results from 2 methods to measure glucose in tracheobronchial aspirates, (2) the effect of blood glucose levels on tracheobronchial glucose levels, and (3) the relationship between results from 2 methods to measure glucose in selected enteral formulas. DESIGN: Descriptive. SETTING: Two midwestern acute-care hospitals, a research laboratory, and a clinical laboratory. PATIENTS: Sixty-two acutely ill adult subjects with artificial airways whose secretions required frequent suctioning for therapeutic purposes; 53 of these 62 patients also required capillary blood glucose measurements for therapeutic purposes. OUTCOME MEASURES: Glucose concentrations in tracheobronchial secretions, capillary blood, and selected enteral formulas. INTERVENTION: None. RESULTS: Measures of glucose content made on 75 split samples of tracheobronchial secretions by 2 methods (glucose oxidase reagent strips and a laboratory assay) were highly correlated (ri = 0.94; P < .001) and mean readings were not statistically different (P = .17). Sixty-six capillary blood glucose readings made within 5 minutes of tracheobronchal suctioning correlated poorly with the glucose content in the tracheobronchial aspirates (r = 0.12; P = .36). Glucose concentrations in 22 enteral formulas determined by 2 methods correlated highly (r = 0.95; P < .001). Glucose concentrations were higher with the laboratory assay (259.6 +/- 206.3 mg/dL) than with glucose oxidase reagent strips (188.6 +/- 157.5 mg/dL). CONCLUSION: It appears appropriate to use glucose oxidase reagent strips to estimate glucose concentrations in tracheobronchial fluid. Elevated blood glucose levels apparently do not have a major effect on the glucose content in tracheobronchial fluid. Although mean glucose concentrations in the 22 formulas were higher with the laboratory assay, the readings were sufficiently similar to allow using glucose oxidase reagent strips to give a good estimation of the formulas' glucose content.

Adult↗

Quality control in urinalysis.

Quality control (QC) has been introduced in laboratories, and QC surveys in urinalysis have been performed by College of American Pathologist, by Japanese Association of Medical Technologists, by Osaka Medical Association and by manufacturers. QC survey in urinalysis for synthetic urine by the reagent strip and instrument made in same manufacturer, and by an automated urine cell analyser provided satisfactory results among laboratories. QC survey in urinalysis for synthetic urine by the reagent strips and instruments made by various manufacturers indicated differences in the determination values among manufacturers, and between manual and automated methods because the reagent strips and instruments have different characteristics, respectively. QC photo survey in urinalysis on the microscopic photos of urine sediment constituents indicated differences in the identification of cells among laboratories. From the results, it is necessary to standardize a reagent strip method, manual and automated methods, and synthetic urine.

Automation↗

Measurement of urinary concentration: a critical appraisal of methodologies.

The measurement of urine concentration provides information concerning the kidney's ability to appropriately respond to variations in fluid homeostasis. It also assists in the interpretation of other tests performed on the same urine specimen. The gold standard of estimating urinary concentration is the measurement of its osmolality; however, this procedure is not readily available to the practicing physician. Therefore, urine concentration is usually determined by measurement of its specific gravity (SG), which provides a fair estimate of urine osmolality. Over the years numerous tests have been developed to measure urine SG in a simple, quick, reliable and easily available method. These tests measure SG either directly (e.g., gravimetry) or by indirect methods (e.g., refractometry and reagent strip). All these tests have certain limitations based on their underlying physical principles. Specific gravity as measured by refractometry is influenced by proteinuria, such that for each 10 g/l protein the SG increases by 0.003. SG is also influenced by glucosuria such that it increases by approximately 0.002 per 10 g/l glucose when compared with urinary osmolality. Unlike osmolality, which is only affected by the number of particles, refractometry is affected by number, mass and chemical structure of the dissolved particles; hence large molecules like radiographic contrast or mannitol will increase SG relative to osmolality. The reagent strip is minimally affected by glucose, mannitol or radiographic contrast. However, it is affected by urinary pH such that only urine in the pH range of 7.0-7.5 can be correctly interpreted. The measurement of SG by reagent strip is based on the ionic strength of the urine and thus is significantly affected by the ionic composition of the urine and by proteins which have an electric charge in solution. In our experience, SG measured by the refractometer is consistently more accurate than the reagent strip. For the clinician who is interpreting urine SG results, it is important to be aware of these limitations and understand the reasons for possible potential errors of each particular method.

Humans↗

Fetal scalp and umbilical artery blood lactate measured with a new test strip method.

OBJECTIVE: To compare the measurement of lactate in fetal scalp and umbilical artery blood by a new dry reagent strip method with a commercially available enzymatic method using plasma (Monotest). DESIGN: Comparative study. SUBJECTS: Fetal scalp blood samples were obtained during labour from 24 fetuses and umbilical artery blood samples were obtained at birth in a further 51 deliveries. RESULTS: The concentration of lactate in scalp and umbilical artery blood measured by the reagent strip method correlated well (r = 0.94, P less than 0.001 and 0.95, P less than 0.001 respectively) with the enzymatic plasma method. The paper strip method tended to give lower readings than the enzymatic method when the fetal haematocrit was greater than or equal to 50%. CONCLUSIONS: The new dry reagent strip method which takes only 1 min to carry out and requires only 20 microliters of blood seems to be handy and reliable. This system provides a convenient and rapid test for measuring fetal blood lactate.

Evaluation Studies as Topic↗

Usefulness of urine strip test in the rapid diagnosis of spontaneous bacterial peritonitis.

PURPOSE: Rapid and accurate diagnosis of spontaneous bacterial peritonitis (SBP) is mandatory for timely treatment in cirrhotic patients. The purpose of this study was to assess the usefulness of two different reagent strips, the UriSCAN and the Multistix10SG, for the rapid bedside diagnosis of SBP. METHODS: A total of 75 paracenteses in 53 cirrhotic patients with ascites were performed. All ascitic fluid was analyzed with the two reagent strips, and compared with the manual cell count with differential and ascitic fluid culture. SBP was defined as an ascitic polymorphonuclear cell count > or =250/mm3. RESULTS: SBP was diagnosed in 18 of the 75 samples. If we considered the positive UriSCAN result of 2 or more, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were all 100%. When we considered the positive UriSCAN result of 3, the sensitivity, specificity, PPV, and NPV were 67%, 100%, 100%, and 89%, respectively. When we considered the positive Multistix10SG result of 3, the sensitivity, specificity, PPV, and NPV were 50%, 100%, 100%, and 87%, respectively. CONCLUSION: Urine reagent strip might be useful for rapid and accurate diagnosis of SBP in cirrhotic patients with ascites.

Ascitic Fluid↗

[Urine test strips for cerebrospinal fluid diagnosis of bacterial meningitis].

BACKGROUND: Diagnosis of bacterial meningitis is due to granulocytic pleocytosis of CSF. In developing countries and in hospitals without continuous availability of a clinical laboratory a bedside-method of diagnosing meningitis is desired. METHODS: 75 CSF samples were tested for granulocytes and protein with reagent strips and the results were compared with those obtained from the clinical laboratory. RESULTS: All 48 samples with normal cell count were correctly diagnosed negative using reagent strips. Twenty-five samples of 27 samples with granulocytic pleocytosis were correctly recognised as right positive (sensitivity 92.6%; specificity 100%). All 48 samples with normal protein were correctly tested normal. Twenty-one samples of 27 samples with elevated protein were correctly diagnosed right positive (sensitivity 77.8%; specificity 100%). CONCLUSION: Testing CSF for granulocytes and protein with urine reagent strips is a bedside-method which allows a rapid and reliable decision whether CSF is normal or granulocytically pleocytotic.

Cerebrospinal Fluid Proteins↗

Asymptomatic bacteriuria in adolescent girls: II. Screening methods.

Of 500 asymptomatic adolescent girls who were screened for bacteriuria by three methods-dipslide (Uricult), dipstrip (Microstix-3 reagent strips), and home nitrite test (Microstix-Nitrite reagent strips)-eight cases (1.6%) were detected: 6/8 by dipslide and dipstrip; 5/8 by nitrite testing. The false-positive-rate (greater than 10(4) colonies/ml) of the dipslide test was 6.4%, and the dipstrip test, 2.8%. A history of vaginal discharge was not associated with "contaminated" specimens. False-positive nitrite tests were reported by 0.6% of the patients who returned the postcards. Overall, 70.4% of the patients returned the postcards for the home nitrite test. The patients were divided by method of payment (Medicaid vs non-Medicaid) in order to provide an approximation of socioeconomic status; non-Medicaid patients were significantly more likely to return postcards than Medicaid patients (75.8% vs 63.7%). Of the group reporting previous urinary tract infection, 79% of both Medicaid and non-Medicaid patients returned postcards, suggesting that a prior experience with the diagnosis increased compliance with a home test.

Adolescent↗

The diagnostic potential of three indirect tests for urinary schistosomiasis in Nigeria.

Schistosomiasis is one of the major parasitic infections of man in the tropical and subtropical areas of the world. Diagnosis of the disease is usually based on microscopic detection of eggs in excreta which is both laborious and time consuming. In Nigeria, the Government's emphasis on the control of the disease dictates the need for a simple, fast, reliable and affordable diagnostic test for the identification of infected communities and detection of infected persons. Three indirect diagnostic tests for urinary schistosomiasis: interview technique, visual examination for macrohaematuria and the use of a chemical reagent strip were employed in screening 1056 individuals of the Kainji Lake area of Nigeria for urinary schistosomiasis, using haematuria as the disease indicator. The sensitivity of the three tests were determined using the filtration (egg counting) technique as the reference test. The sensitivity of the reagent strip test was 69.0% and 44 and 38% for the interview technique and visual examination respectively. The reagent strip test was particularly useful for screening children (5-19 years old). The implication of these findings are discussed.

Adolescent↗

Test-strip method for measuring lactate in whole blood.

We have developed a dry reagent strip system for measuring lactate in whole blood. The test strip contains lactate oxidase (no EC number assigned), horseradish peroxidase (EC 1.11.1.7), and N-ethyl-N-(2-hydroxy-3-sulfopropyl)-m-toluidine. The system is designed to measure with a reflectometer the color that developed in the test strip, although the lactate concentration can be estimated without the reflectometer. The between-run coefficients of variation for controls at three concentrations were 2.9-5.3%. The lactate concentrations in blood samples from healthy subjects before and after exercise correlated well (r = 0.97) with the results measured by the comparison method with the use of lactate oxidase. This dry reagent strip system provides a convenient and rapid test for measuring blood lactate in clinical and sports medicine.

Horseradish Peroxidase↗

[Delayed evaluation of test strips for blood glucose determination in small reflectometers].

The precision and accuracy of reacted reagent strips (Haemoglucotest 20-800 R, Reflocheck) stored in an envelope and analysed 24 and 48 hours later, by means of glucose reflectance meters (Reflolux II, Reflocheck) was studied. A good correlation of the values estimated after 24 and 48 hours to the value analysed immediately after sampling was found for both systems (Reflolux II 24 hours later, r = 0.9713, y = 24.16 + 0.7369. x, and 48 hours later, r = 0.9388, y = 44.21 + 0.5234. x; Reflocheck 24 hours later, r = 0.977, y = 9.72 + 0.9525. x, and 48 hours later, r = 0.9433, y = 45.97 + 0.4802. x). Our data show, that the initial value can be calculated using the 24 and 48 hour values by means of linear regression. Therefore the analysis of reacted reagent strips for blood glucose determination is beneficial in the management of Typ-I-Diabetics.

Blood Glucose↗

A comparison of accuracy and estimated cost of methods for home blood glucose monitoring.

Venous serum glucose concentrations determined by a laboratory hexokinase technique were compared over a wide range of glucose concentrations with concentrations of capillary blood glucose determined by three reflectance meter techniques currently available in the United States (Eyetone and Dextrometer, Ames Company; StatTek, Bio-Dynamics BMC) and by visual interpretation of reagent strips (Chemstrip bG, Bio-Dynamics BMC). The Chemstrip bG reagent strip was read by patients, nurses, and a physician. In all cases, there was an excellent correlation between laboratory serum glucose concentrations and reflectance meter blood glucose determinations (r = 0.90-0.94, P less than 0.0001) or visual interpretation of Chemstrip bG (r = 0.85-0.92, P less than 0.0001). Chemstrip bG appears to be the least expensive method of glucose measurement. This method offers additional advantages in not requiring a reflectance meter, which needs frequent recalibration and other ancillary equipment for blood glucose determination.

Blood Glucose↗