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Rapid diagnosis of infectious pleural effusions by use of reagent strips.

Reagent strips have not yet been tested for use in the diagnosis of infectious pleural effusions. A reagent strip was used to evaluate 82 patients with pleural effusions: 20 patients had transudative effusions, 35 had infectious exudative effusions (empyema in 14 and parapneumonic effusion in 21), and 27 had noninfectious exudative effusions. Pleural fluid protein, as evaluated by the reagent strip, proved accurate for the detection of exudative effusions (sensitivity, 93.1%; specificity, 50%; positive predictive value, 84.3%; negative predictive value, 71.5%; odds ratio [OR], 6.77; and 95% confidence interval [CI], 1.87-24). The reagent strip leukocyte esterase test effectively detected infectious exudative effusions (sensitivity, 42.8%; specificity, 91.3%; positive predictive value, 88.2%; negative predictive value, 51.2%; OR, 4.46; and 95% CI, 1.2-16.4). Pleural pH was significantly predicted by the reagent strip but was of no assistance in categorization of exudative effusions as infectious or noninfectious. Compared with physical, laboratory, and microbiological data, the reagent strip was as accurate for estimation of percentages of infectious and noninfectious exudative effusions. Thus, reagent strips may be a rapid, easy-to-use, and inexpensive technique for discriminating transudative from exudative pleural effusions and for categorizing exudative pleural effusions as infectious or noninfectious.

Adult↗

Guidelines for evaluation of reagent strips. Exemplified by analysis of urine albumin and glucose concentration using visually read reagent strips. International Federation of Clinical Chemistry, Scientific Division.

Reagent strips are frequently used in the practice of laboratory medicine as well as outside the professional laboratories. In the present report, a scheme is presented which allows a reproducible description of the performance of reagent strips. This is exemplified using strips intended for estimation of urinary albumin and glucose. Experimental conditions that are particularly important for these components are given. Suitable and necessary items which should be included in the protocol presenting results of an evaluation are listed. The guidelines might have general applicability in evaluation and description of tests with a limited number of possible results.

Albuminuria↗

Blood glucose reagent strip tests in the operating room: influence of hematocrit, partial pressure of oxygen, and blood glucose level--a comparison of the BM-test 1-44, BM-Accutest, and Satellite G reagent strip systems.

OBJECTIVE: The objective of our study was to assess the influence of hematocrit (HCT), partial pressure of oxygen (PO2), and blood glucose level upon results obtained with three different blood glucose reagent strip tests used in conjunction with the appropriate meter: BM-Test 1-44, BM-Accutest, and Satellite G. METHODS: Our study was designed as a consecutive sample study of patients undergoing coronary artery surgery. The setting was the hospital theater and intensive care unit. We conducted blood analysis for HCT, PO2 and blood glucose on 20 consecutive patients undergoing coronary artery surgery using three blood glucose reagent strip testing systems and a laboratory analysis of plasma glucose. RESULTS: All three blood glucose reagent strip tests showed a significant bias when compared with plasma glucose: BM-Test 1-44, 0.89 mmol/L; BM-Accutest, -1.27 mmol/L; Satellite G, 0.75 mmol/L (p < 0.05). The error found when using the Satellite G system was worse than that of either of the other two systems. Results obtained with the BM-Accutest strips were unaffected by PO2 (p = 0.745). Blood glucose value and HCT both had an influence on the results of all three blood glucose strip systems. CONCLUSIONS: Caution must be taken when using reagent strip systems in the operating room or intensive care setting because, of the three systems tested, all showed a significant bias, all were influenced by blood glucose level and HCT, and only the BM-Accutest reagent strips used with the Accutrend meter was unaffected by PO2.

Bias↗

Accuracy of blood glucose concentrations determined by four visually read reagent strips.

Two new reagent strips have recently been introduced for blood glucose measurement by direct visual reading. Results obtained with these strips (Glucostix and Hypogard GA) were compared with those obtained using other commonly employed strips (BM-Test-Glycemie 1-44 and Visidex II) and a standard laboratory method. Blood glucose estimations were performed on samples of venous blood drawn from 125 patients attending the diabetic clinic using each of the four strips and the laboratory method. Results obtained with the strips correlated with the laboratory values as follows: BM-Test-Glycemie 1-44, r=0.93; Glucostix r=0.93; Hypogard GA r=0.87 and Visidex II r=0.92. The lower correlation with Hypogard GA reflected consistent underestimation of the laboratory value (slope of regression line = 0.63). Readings in error by 20% or more were: BM-Test-Glycemie 1-44, 14%; Glucostix, 15%; Hypogard GA, 31%, and Visidex II, 14%. With Hypogard GA strips, 57% of readings above 16 mmol/l were inaccurate. We conclude that Hypogard GA strips cannot be recommended for direct visual reading. Acceptable results may, however, be obtained using the other three strips.Reagent strips allow reasonably accurate determinations of blood glucose concentrations when used with a reflectance meter.(1, 2) Nevertheless many diabetic patients prefer to read the reagent strips visually. This method avoids the problems associated with meter calibration, is cheaper and also is more portable. Direct visual readings with BM-Test-Glycemie 1-44 (Boehringer Corporation) and Visidex II (Ames) have been shown to be acceptable in the hands of medical and technical personnel.(3, 4) Recently two new reagent strips have been marketed, Hypogard GA (Hypogard UK Ltd) and Glucostix (Ames), and it is claimed that they are also suitable for direct visual reading. To test the validity of these claims, we have compared results obtained using the newer strips with readings from BM-Test-Glycemie 1-44 and Visidex II and with a standard laboratory method.

Blood Glucose↗

Study of urinary specific gravity by reagent strip method.

A newly developed reagent strip method for determination of urinary specific gravity is described. This reagent strip (Chemical S.G., Ames Co.) contains polyelectrolyte which is sensitive to the cation in solution. The urinary specific gravity is mainly decided by cation (Na+ and K+) concentrations in urine. As a result, the reagent strip gave measurements that corresponded to those measured by refractometry and gravimetry of NaC1 solution. Urea and glucose gave increased values by the refractometer, whereas the reagent strip did not cause changes. The values of urinary specific gravity obtained from reagent strip showed not only good correlations (r = 0.79-0.93) with the refractometry and gravimetry but also urinary osmolarity. This reagent strip method proved to be a most convenient tool for routine urinalysis because of the good reproducibility and accuracy considering its easy handling.

Contrast Media↗

Characteristics of a new urine, serum, and saliva alcohol reagent strip.

We have tested an ethanol reagent strip developed at the Addiction Research Foundation of Ontario. Alcohol dehydrogenase and nicotinamide adenine dinucleotide, in the presence of pyrazole, react with ethanol to yield acetaldehyde plus reduced nicotinamide adenine dinucleotide. The latter reduces iodonitrotetrazolium chloride in the presence of diaphorase, generating an intense red color. The rate of color development is proportional to the concentration of ethanol. Color is compared at a specific time against a calibrated color scale ranging from green (negative) to red, representing alcohol concentrations of 0, 25, 50, 100, 200, and 400 mg/dl (0-0.4%; 0-87 mmol/liter). We were able to interpolate the color observed between the calibrated blocks. When tested on urine, serum/plasma, and saliva, ethanol concentration determined by the reagent strip correlates well with ethanol concentration as determined by gas chromatography or by automated enzymatic analysis (r = 0.92-0.98, p less than 0.001; slope 0.83-1.16). The reagent strip was shown to be used appropriately by nonexperienced individuals following a 1-min explanation (reagent strip values, r = 0.92; p less than 0.001, slope = 0.97, versus gas chromatography). The reagent strip does not react with methanol (wood alcohol), isopropanol (rubbing alcohol), and ethylene glycol (antifreeze) often found in accidental poisonings. In 379 clinical samples obtained without exclusion criteria from 12 hospital emergency rooms and a liver clinic, the sensitivity of the reagent strip in detecting ethanol was 98%. Specificity was 99%. The reagent strip was found to have virtually unlimited stability under refrigeration (4 degrees C) and to be stable for 3 to 4 months at room temperature (22-23 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗

Rapid diagnosis of spontaneous bacterial peritonitis by use of reagent strips.

We studied the use of reagent strips for diagnosis of spontaneous bacterial peritonitis (SBP) in cirrhotic patients with ascites. A reagent strip for leukocyte esterase designed for the testing of urine with a colorimetric 5-grade scale (0 to 4) was used to evaluate ascitic fluid in 228 nonselected paracentesis performed in 128 cirrhotic patients. We diagnosed 52 SBP and 5 secondary bacterial peritonitis by means of polymorphonuclear cell count and classical criteria. When we considered positive a reagent strip result of 3 or 4, sensitivity was 89% (51 of 57), specificity was 99% (170 of 171), and positive predictive value was 98%. When we considered positive a reagent strip result of 2 or more, sensitivity was 96% (55 of 57), specificity was 89% (152 of 171), and negative predictive value was 99%. In conclusion, the use of reagent strips is a rapid, easy to use, and inexpensive tool for diagnosis of ascitic fluid infection. A positive result should be an indication for empirical antibiotic therapy, and a negative result may be useful as a screening test to exclude SBP.

Aged↗

The detection of leukocyte esterase activity in urine with a new reagent strip.

An evaluation of the Ames Leukostix reagent strips for the detection of leukocyte esterase activity in urine was undertaken to determine the interlot precision and between reader reliability, to compare Leukostix and Chemstrip LN results, and to determine if the Ames Leukostix reagent strip provides an alternative to, or supplement for, the microscopic detection of leukocytes. A total of 412 urines were analyzed with the Ames and Bio-Dynamics reagent strips. The sensitivity and specificity of Leukostix results, relative to a quantitative chamber count, were 89.4% and 90.4%, respectively. Chemstrip LN provided essentially the same results with a sensitivity of 88.8% and specificity of 92.4%. The between-reader and between-lot reproducibility was excellent, with 99% of the results agreeing within half a color block of each other. The sensitivity of the sediment count relative to the chamber count was 68.9% and the specificity, 97.7%. Performance of the sediment count in addition to use of the reagent strip provided little additional information. On the basis of these results, the Ames Leukostix reagent strip is considered to be a suitable alternative to sediment microscopic examination for the detection of leukocytes in urine.

Esterases↗

[Diagnosis of meningitis with reagent strips]

OBJECTIVE: To determine the usefulness of reagent strips in the evaluation of pleocytosis, cerebrospinal fluid glucose and protein levels for early and rapid diagnosis of meningitis in children. METHODS: We included cerebrospinal fluid samples of 164 children admitted to the outpatient clinic of Communicable Diseases of the General Pediatric Center (Fundação Hospitalar do Estado de Minas Gerais, CGP-FHEMIG) during the daytime hours from May of 1997 to May 1999, and who presented with clinical suspicion of meningitis. Patients ranged in age from one month to 12 years (median 12 months). Results from the cytological and biochemical assay (cellularity, cerebrospinal fluid glucose and protein levels) were obtained from 154 patients. These results were subsequently compared with the reaction of cerebrospinal fluid in reagent strips. RESULTS: The cytological and biochemical assay identified 43 cases of probable bacterial meningitis, 19 of probable viral meningitis, and 83 with no alterations. According to the reagent strips, there were 41 cases of probable bacterial meningitis, 2 of probable viral meningitis, and 71 with no alterations. By comparing the results of reagent strips and those of the cytological and biochemical assay, we obtained values for sensitivity, specificity, positive and negative predictive values, and accuracy (respectively 90.7; 98.1; 95.1; 96.4; and 96.1). Statistical analysis using McNemer test did not indicate significant differences between the two methods in the diagnosis of bacterial meningitis (P=0.68). Kappa statistics indicated a high level of agreement between the tests (P<0.0001). CONCLUSIONS: Our results suggest that reagent strips may be a useful additional resource in the diagnosis of bacterial meningitis, especially when it is difficult to collect a sufficient amount of cerebrospinal fluid or to indicate the initial treatment.

Journal Article↗

[Dry chemistry of reagent strips].

Quantitative analysis with dry reagent strips for the determination of clinical chemistry parameters and drug monitoring in serum, plasma and whole blood is expanding in small laboratories and in office laboratories. The systems predominantly used are Ektachem DT 60, the Seralyzer and the Reflotron. - The methods offered comprise substrates, enzymes, electrolytes, CO2 and drugs. The spectrum of feasible tests varies with the manufacturer. On the whole all the tests commonly used in small laboratories are covered. The instruments used for quantitative dry reagent strip chemistry are calibrated by the manufacturer. Calibration data are either inputted to the instrument with each method or already programmed in the apparatus. Thus calibration is outside the control of the user, a change of philosophy which does not correspond to present concepts of quality control in clinical chemistry. The analytical precision is satisfactory for all three instruments for the common parameters measured. A comparison between "dry-chemistry" determinations and the classical aqueous analyses show good accuracy as long as patient samples are used. This is, however, not true for all reference materials, presumably due to matrix effects. Our own evaluation of the Seralyzer showed a good correlation of potassium analysis compared with flame photometry; this was also true of gamma-glutamyltransferase using the Reflotron with patient samples. Internal quality control can only be performed with materials assessed by the instrument manufacturers, and the results will often differ for these materials when assayed with conventional methods or with other "dry-chemistry" methods. External quality control also has its limitations due to the fact that no sera are available which could be used universally.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemistry, Clinical↗

Accuracy of reagent strips in detecting hypoglycemia in the emergency department.

STUDY OBJECTIVE: Although reagent strips are commonly used, their reliability to estimate blood glucose concentration and guide administration of dextrose solutions in the emergency department environment has not been proved. We determined the accuracy of visually interpreted reagent strips (Chemstrip bG, Boehringer Mannheim Corp, Indianapolis, IN) and their ability to identify hypoglycemic patients in the ED. METHODS: We conducted a prospective, nonrandomized blinded clinical study of the visual estimation of blood glucose values by ED personnel using Chemstrip bG reagent strips during a 4-month period. Simultaneously obtained blood samples sent for laboratory glucose determination served as controls. The study was conducted at a large university hospital ED with an urban patient population. A convenience sample of 215 adult ED patients underwent serum glucose determination with data form completion. No study intervention was tested, although timing of administration of dextrose solutions, if given, was recorded. RESULTS: Hypoglycemia was defined as a glucose concentration less than 60 mg/dL on standard laboratory analysis. Reagent strips identified 28 of 29 of these patients (sensitivity=97%), and 171 of 182 patients without hypoglycemia (specificity=94%, negative predictive value=99%) compared with control samples. The 1 false-negative reagent strip reading of 80 mg/dL was obtained from blood stored in a serum separator tube and had a laboratory glucose value of 39 mg/dL. Eighty-seven percent of the reagent strips were within +/-60 mg/dL of the control value for the laboratory glucose reference range less than 350 mg/dL. CONCLUSION: Visually interpreted Chemstrip bG reagent strips provide an acceptable estimation of blood glucose concentration in the ED and are highly sensitive in detecting hypoglycemia.

Adult↗

Clinical evaluation of commercial reagent strips for detection of significant bacteriuria in dogs and cats.

The reagent strip technique of quantitative urine culture was a satisfactory screening test for the detection of significant bacteriuria in dogs and cats. The reagent strip technique was found to be of almost equal sensitivity as the calibrated loop technique in identifying significant bacteriuria. Significant bacteriuria was detected in 38 of 148 urine samples evaluated by the calibrated loop technique. Of these 38 urine samples, significant bacteriuria was detected in 35 by the commercial test. False-negative results were obtained with reagent strips in 1 urine sample which had significant bacteriuria by the calibrated loop technique. The other 2 samples had bacterial counts of suspicious significance (10,000/ml of urine) by the reagent strip technique. False-positive results were obtained with the reagent strip technique in 3 urine samples; however, all 3 urine samples had bacterial counts (10,000/ml of urine) of suspicious significance when evaluated by the calibrated loop technique. The reagent strip technique was not satisfactory for the examination of patients with gross hematuria. The nitrite test portion of the commercial test did not detect significant bacteriuria in all samples and, therefore, was not suitable as a screening test for significant bacteriuria in dogs and cats. The nitrite test may have been inhibited by ascorbic acid, a metabolite which normally may exist in the urine of these animals.

Animals↗

Rapid diagnosis of schistosomiasis by antigen detection in urine with a reagent strip.

For the rapid and simple diagnosis of schistosomiasis, a reagent strip assay for detection of circulating cathodic antigen (CCA) in urine was developed. The test was based on a previously developed sandwich enzyme-linked immunosorbent assay (ELISA) using a combination of two anti-CCA monoclonal antibodies. For the reagent strip assay, as the capture matrix, monoclonal antibody was coated onto a nitrocellulose membrane and mounted on polyvinyl chloride strips. Urine samples were then tested in an assay consisting of a combined incubation step of the urine sample and biotinylated detecting antibody followed by incubation in streptavidin peroxidase and a subsequent staining. The specificity and the sensitivity of the assay, as determined with urine samples of 61 uninfected controls and 67 Schistosoma mansoni-infected individuals, were 96.7 and 95.5%, respectively. The results of the reagent strip assay compared very well with microscopical parasitological diagnosis by the standard Kato-Katz method for the same individuals. The reagent strip test has a lower detection limit of 1 ng of CCA per ml and can be completed in 75 min. By the inclusion of two reference bands on the strips, standardized reading could be achieved. This reagent strip assay is a promising tool for qualitative diagnosis of S. mansoni infections in control programs.

Animals↗

Simultaneous use of a sensitive filtration technique and reagent strips in urinary schistosomiasis.

A sensitive filtration technique and polyvalent urine analysis reagent strips were used simultaneously in patients with urinary schistosomiasis in order to detect pathological conditions other than haematuria and proteinuria. A significant correlation was found between haematuria, proteinuria, leucocyturia and intensity of infection as measured by egg excretion in urine. The best correlation between the reagent strip findings and intensity of infection was obtained when the three parameters were combined. After treatment with metrifonate the reduction of egg excretion was paralleled by the normalization of the reagent strip findings. Analysis of day-to-day variation demonstrated a similar low variation of the filtration technique and the reagent strip findings. Specificity of urine analysis of reagent strips was tested in two age-matched control groups. Although the study was designed only as a pilot study, the results suggests that polyvalent reagent strips may be a useful tool for diagnosis of heavily infected patients under field conditions, as they permit rapid and easy identification of subjects with high egg counts.

Child↗

Laboratory, nurse and patient assessment of Glucostix blood glucose reagent strips.

The new Glucostix (Ames) blood glucose reagent strips have been assessed for accuracy and acceptability by nurses using them on the ward and by patients at home. When used with a Glucometer II, Glucostix showed close correlation with blood glucose measured by Yellow Springs Analyser (r = 0.97, p less than 0.001). Using the strips without a meter patients achieved a good correlation with the Yellow Springs Analyser when measuring their own capillary blood glucose (r = 0.94, p less than 0.001). Ward nurses were less precise (r = 0.87, p less than 0.001) and this, perhaps, reinforces the importance of regular quality control to maintain the precision of blood glucose monitoring using reagent strips. Comparing Glucostix with BM Glycemie 1-44 strips, 14 of 15 nurses preferred Glucostix whereas patients showed no overall preference, 37% preferring BM Glycemie 1-44, 33% Glucostix, and 30% stating no preference. There were only minor differences between the two reagent strips. Both groups considered the Glucostix colour change to be easier to read, particularly when using the perforated bench readers, but some thought Glucostix needed more blood and that it was more difficult to remove from the pad. Thus, the Glucostix system provides an accurate measure of blood glucose and is an acceptable alternative to BM Glycemie 1-44 strips for use at home or on the ward.

Adult↗

Bedside diagnosis of spontaneous bacterial peritonitis using reagent strips.

OBJECTIVE: To determine the efficacy of reagent strip for bedside diagnosis of spontaneous bacterial peritonitis (SBP). DESIGN: Cross-sectional analytical study. PLACE AND DURATION OF STUDY: Shaikh Zayed Postgraduate Medical Institute from November 2003 to August 2004. PATIENTS AND METHODS: Patients with cirrhosis and ascites underwent diagnostic paracentesis. Fluid was checked for leukocyte esterase released by PMN by using Combur 10 urine strip and graded for color change from 0-3. Fluid was also analyzed by cytology for PMN count. Results of both methods were compared to determine sensitivity, specificity and accuracy of strip for diagnosis of SBP. RESULTS: Of 214 paracentesis performed, SBP was diagnosed in 38 patients whereas 176 were negative for infection. Strip test was 97.7% sensitive and 89.4% specific with positive predictive value of 90%, negative predictive value of 97.7% and accuracy of 96.2%, when reagent strip grade 3 was considered as positive for diagnosis. CONCLUSION: Reagent strip is a quick bedside test, highly sensitive and specific for the diagnosis of SBP, based on polymorphonuclear count in ascitic fluid, to initiate early treatment, thus improving patient's outcome.

Adult↗

A reagent strip for measuring the specific gravity of urine.

A solid-phase reagent for determination of urinary specific gravity (relative density) is described. This reagent strip, similar to others in the "N-Multistix" series (Ames), contains a polyacid whose acidity is sensitive to the ionic concentration in the urine in which it is immersed. As the acidity of the polyacid changes, pH changes are detected by a pH indicator within the reagent strip. In comparison studies, 84.4% of relative densities as measured with these reagent strips were within 0.005 of the corresponding results with a total-solids meter, and 89.9% were within 0.005 of the corresponding urinometer results. Adding a correction of +0.005 to the reagent-strip results for urines with high pH increased the percentage of results within 0.005 of the comparison method to 90.7% (TS meter) and 92.9% (urinometer). Lot-to-lot variability and reader-to-reader variability were both low. Reagent strip results are not affected by glucose, may be increased by albumin, and correlate with urea concentrations.

Equipment and Supplies↗

Utility of urine reagent strip in screening women with incontinence for urinary tract infection.

The aim of this study was to determine the utility of urine reagent strips in screening women with urinary incontinence for urinary tract infections. Subjects were all women presenting with urinary incontinence. A urine specimen was screened for urinary tract infection with a urine reagent strip and urine culture. Using the urine culture result as the gold standard, the sensitivity, specificity, and positive and negative predictive values of the urine reagent strips were calculated. A total of 265 pairs of reagent strips and urine cultures were evaluated. Thirty-one cultures grew out of a single organism; nine of these had a positive urine reagent strip, yielding a sensitivity of 29%. The specificity of the urine reagent strip was 99%, the positive predictive value was 82% and the negative predictive value was 92%. For women presenting with urinary incontinence, the sensitivity of a urine reagent test for diagnosing urinary tract infection was low.

Bacteriological Techniques↗