Strip Test Results Research Articles

Reliability of using reagent test strips to estimate blood urea nitrogen concentration in dogs and cats

To evaluate the clinical accuracy of reagent test strips used to estimate BUN concentration in dogs and cats. Prospective study. 116 dogs and 58 cats. Blood samples were collected at the time of admission to the hospital. Estimates of BUN concentration obtained with reagent test strips (category 1 [5 to 15 mg/dL], 2 (15 to 26 mg/dL], 3 [30 to 40 mg/dL], or 4 [50 to 80 mg/dL]) were compared with SUN concentrations measured with an automated analyzer. For dogs, category 1 and 2 test strip results were considered a negative result (nonazotemic) and category 3 and 4 test strip results were considered a positive result (azotemic). For cats, category 1, 2, and 3 test strip results were considered a negative result (nonazotemic) and category 4 test strip results were considered a positive result (azotemic). On the basis of SUN concentration, 40 of the 174 (23%) animals (20 dogs and 20 cats) were classified as azotemic. One dog and 2 cats had false-negative test strip results, and 1 dog had a false-positive result. Sensitivity and specificity were 95% (20/21) and 99% (94/95), respectively, for dogs and 87% (13/15) and 100% (43/43), respectively, for cats. Results suggest that reagent test strips are a reliable method for rapidly estimating BUN concentrations in dogs and cats. Because test strip results are only semiquantitative and there remains a potential for misclassification, especially in cats, urea nitrogen concentration should ultimately be verified by means of standard chemistry techniques.

Development of a Rapid Immunochromatographic Strip for Detection of Escherichia coli O157

We developed an immunochromatographic (IC) strip for the rapid detection of Escherichia coli O157 in enriched samples. Murine monoclonal antibody to E. coli O157:H7 lipopolysaccharide was conjugated with 40nm of colloidal gold particles by the citrate method. The specificity of the IC strip was determined using 48 pure-cultured bacteria, including 32 E. coli strains and 16 non–E. coli strains. Regardless of H serotype, E. coli O157 strains produced a positive signal, whereas the others, representing 29 E. coli serotypes, did not. Among 16 non–E. coli strains, only Citrobacter amalonaticus yielded a positive signal. The sensitivity of the IC strip was determined using 10-fold diluted E. coli O157:H7, with a range of 1.8 × 107 to 1.8 CFU/ml in enriched raw beef. E. coli O157 could be detected at a minimum of 1.8 × 105 CFU/ml without enrichment and 1.8 CFU/ml after enrichment. Various samples were enriched to detect E. coli O157 using the IC strip and to isolate E. coli O157:H7 using traditional culture procedures. The IC strip test results exhibited 100% agreement with traditional methods after selective enrichment, since E. coli O157:H7 was also isolated from all the samples with positive strip test results. However, the specificity of the strip was somewhat higher with pork (98.8%) than with bovine feces (87.9%) and swine feces (93.4%). These results indicated that the IC strip exhibits high specificity and sensitivity in the detection of E. coli O157, and this assay is rapid, economical, and simple, without requirement of complicated equipment.

Urine analysis and decision-making on cystitis in general practice

Decision-making on cystitis in general practice was studied by addressing 1171 general practitioners of whom 909 responded. A case history was supplied with a test-strip result where leucocyte esterase was 1+ and the nitrite field either positive or negative. The respondents' estimated probability of urinary tract infection from the history had a median at 50% (10 and 90 percentiles, 30% and 90%). The test-strip results changed the estimate to 90% (50% and 100%) in the nitrite-positive group and 50% (10% and 90%) in the nitrite-negative group. Likelihood ratio was calculated from each respondent's estimated pre- and post-test probability to express the test's assumed diagnostic power. The median likelihood ratios were 4.75 (10 and 90 percentiles, 1.00 and 35.70) in the nitrite-positive group and 1.00 (0.11 and 4.00) in the nitrite-negative group. The resulting actions taken by the respondents were: no action (14 respondents, corresponding median estimated post-test probability 27.5%), await further examination (482, 50%) and prescription of antibiotics (366, 90%). Further examination included urine microscopy (13%), bacteriologic culture (21%), or both (65%). Eight-two percent of respondents who decided to prescribe antibiotics would also perform further examinations. In routine urine analysis, 79% of respondents request only test strips, 2% perform microscopy and 19% do both. The estimated probability of urinary tract infection is significantly affected by test-strip results and is important for the choice of further actions. Microscopy is performed more often than recommended in other studies.

Assessment of a pyrogallol red technique for total protein measurement in the cerebrospinal fluid of dogs

The measurement of protein concentration in the cerebrospinal fluid is a basic analytical method in neurology. In this study, a pyrogallol red technique using a human albumin calibrator previously validated in human medicine was tested for canine samples, and the results were compared with those obtained using urine test strips. Pyrogallol red significantly (P<0.05) but moderately underestimated purified dog albumin and globulins. The imprecision of the technique was low: intra- and between-series coefficients of variation were 1.6 and 4.3 per cent at protein concentrations of about 0.3 g/litre. Over 49 samples, there was good agreement between the pyrogallol red and test strip results (r=0.63), especially for low and high protein concentrations, but misclassifications were observed with '+' test strip readings.

What is the predictive value of urinary symptoms for diagnosing urinary tract infection in women?

Our aim was to determine the probability of correctly diagnosing urinary tract infections (UTIs) from urinary symptoms and signs, studying their sensitivity, specificity and likelihood ratio (LR) when clinical history, signs and reactive strip test results are taken into account. An epidemiological analysis with a diagnostic and clinical orientation was carried out in a primary health care setting. The subjects comprised 343 women > or =14 years of age who consulted their family physician for incident urinary tract symptoms. A guided medical examination was carried out using a check-list formulary, reactive strip test, urine culture and the clinical course of all patients. The pre-test probability of having UTI among patients with incident urinary symptoms is 0.484 [95% confidence interval (CI) 0.431-0.536]. Positive LRs for UTI are: painful voiding 1.31 (95% CI 1.12-1.54), urgency 1.29 (95% CI 1.12-1.50), urinary frequency 1.16 (95% CI 1.06-1.28) and tenesmus 1.16 (95% CI 1.02-1.32). The probability of UTI is reduced by the presence of genital discomfort, dyspareunia, vaginal discharge, positive lumbar fist percussion and perineal discomfort. Nitrites on the urine reactive strip test increase the probability of UTI by >5 times, moderate pyuria increases it by >1.5 times, and the presence of both findings does so by >7 times. In women with urinary symptoms, a thorough clinical examination, together with performance of a reactive strip test during the office visit, improves the chances of detecting UTI.

Semi-quantitative immunochromatographic test for prostate specific antigen in whole blood: tossing the coin to predict prostate cancer?

A strip test for the semi-quantitative determination of prostate specific antigen (PSA) based on whole blood was evaluated by the Working Group on Laboratory Diagnostics of the German Urological Association. In 301 men (156 volunteers and 145 referred patients, mean ages 57 years and 64 years) handling and capability of the strip test to predict PSA serum concentrations (Access Hybritech, Beckman Coulter, Inc., Fullerton, CA, USA) relative to a cutoff of 4 micro g/l were investigated. For patients, the strip test was performed by investigators, volunteers accomplished it according to leaflet instructions. Each test result was interpreted by both, the patient/volunteer and an investigator. 24% of the volunteers required assistance with test performance. The overall agreement between Access PSA (range 0.1-29.7) and strip test was 76% (read by participants) and 79% (read by investigators). Within the PSA ranges 0.1-3, 3.1-5 and 5.1-10, participants yielded agreement rates of 89%, 40% and 56%, respectively. Studying the 2.1-10 PSA range most relevant for prostate cancer screening, agreement rate (53%), sensitivity (50%) and specificity (67%) were barely superior to random chance. Volunteers alone (PSA range 0.1-11.3 micro g/l) yielded a specificity of 92%, however, all PSA values above the cutoff (n=8) went unrecognized and all positive strip tests (n=12) were incorrect (sensitivity 0%, positive predictive value 0%). Test handling and interpretation was difficult. The rate of false strip test results is disappointing even for PSA ranges remote from the cutoff. In its present form the strip test fails to meet the clinical requirements and its launch to the market was therefore discontinued.

Quantitative Evaluation of Urinalysis Test Strips

Urine test strip results are generally reported in categories (i.e., ordinal scaled), but automated strip readers are now available that can report quantitative data. We investigated the possible use of these meters to complement flow cytometry of urine and compared reflectance readings with quantitative determinations of urinary glucose and microalbumin. We compared URISYS 2400 (Roche) quantitative reflectance data with data from the UF-100 (Sysmex) and biochemical data for 436 nonpathologic and pathologic urine samples. Reproducibility of the reflectance signal was good for high- and low-concentration urine pools for protein (0.8% and 0.9% and 1.5% and 2.2% within and between runs, respectively), leukocyte esterase (1.1% and 1.0%; 5.1% and 1.2%), hemoglobin (1.7% and 1.1%; 8.9% and 1.1%) and glucose (2.1% and 0.5%; 6.5% and 2.3%). Fair agreement was obtained between UF-100 and test strip reflectance data for erythrocytes and hemoglobin (r = -0.680) and leukocytes and leukocyte esterase (r = -0.688). Higher correlations were observed for biochemical and test strip data comparing protein and albumin (r = -0.825) and glucose data (r = -0.851). The lower limits of detection for erythrocytes and leukocytes were 8 x 10(6)/L and 19 x 10(6)/L, respectively. The protein test (n = 220) detected 86% (95% confidence interval, 78-92%) of samples with <30 mg/L albumin with a specificity of 84% (95% confidence interval, 76-91%). In urine test strip analysis, quantitative hemoglobin and leukocyte esterase reflectance data are complementary with flow cytometric results and glucose and albumin results.

Evaluation of a dipstick malaria sporozoite panel assay for detection of naturally infected mosquitoes.

The determination of the presence or absence of malaria sporozoites in wild-caught Anopheles mosquitoes remains an integral component to the understanding of the transmission dynamics in endemic areas. To improve that capability, there has been on-going development of a new device using dipstick immunochromatographic technology for simplifying the testing procedure and reducing the time required to obtain results. As part of a larger multi-center effort, we evaluated the sensitivity and specificity of a prototype malaria sporozoite antigen panel assay (Medical Analysis Systems, Camarillo, CA) against three human Plasmodium species/polymorphs. The wicking (dipstick) assay was compared against a standard parasite antigen capture enzyme-linked immunosorbent assay (ELISA) for the detection of human circumsporozoite protein (CSP) in wild-caught mosquitoes. Over 6,800 Anopheles mosquitoes, representing 20 species collected from malaria endemic areas of Indonesia were tested either individually or in pools of up to 10 mosquitoes each. From 1,442 pooled test strip assays and ELISA formats, nine mosquito pools were found reactive for P.falciparum, P. vivax 210, or P. vivax 247 CSP. There was complete concordance between test strip results and ELISA results. Sensitivity was 100% and given some minor problems with false positives or negatives, specificity (n = 488) was 97%. Most strips judged as false positive produced very weak signals compared with negative control blank strips and paired ELISA-negative samples. The dipstick test proved technically simpler to perform and interpret than the ELISA and results were obtained within 15 min of exposure to mosquito suspension. This qualitative assay appears an attractive alternative to the CSP ELISA for detection of sporozoites in fresh or dried mosquitoes.

Reference Values for Neonates and Children for the UF-100 Urine Flow Cytometer

The UF-100 fully automated urine flow cytometer classifies urinary particles on the basis of their light scattering, fluorescence, and impedance properties. The UF-100 counts erythrocytes, leukocytes, bacteria, epithelial cells, and casts. The operating principles of the UF-100 and its precision, accuracy, and analytical sensitivity have been published previously (1)(2)(3)(4). The high sensitivity of the flow cytometer leads to different reference values. In a recent report, Gyory et al. (5) presented reference values for children; for newborns, however, reference values have not as yet been published. In this report, we present preliminary reference values for neonates and children. To establish these reference ranges, samples from two groups of children were analyzed. The pediatricians considered the infants in the first group to have no afflictions of the urinary tract after studying the case history, laboratory values (e.g., creatinine and urea), and the urine test strip results (n = 114). These infants were admitted to the neonatal clinic and remained there for >5 days. Admission automatically included urine examination in daily routine programs without additional consent …

Rapid accurate field diagnosis of Indian visceral leishmaniasis

A firm diagnosis of visceral leishmaniasis (kala-azar) requires demonstration of the parasite in organ aspirates or tissue biopsy samples. The aim of this prospective study was to assess the diagnostic usefulness of non-invasive testing for antibody to the leishmanial antigen K39 by means of antigen-impregnated nitrocellulose paper strips adapted for use under field conditions. One drop of peripheral blood is applied to the hitrocellulose strip. Three drops of test buffer (phosphate-buffered saline plus bovine serum albumin) are added to the dried blood. The development of two visible bands indicates presence of IgG anti-K39. 323 consecutive patients with suspected kala-azar referred to two specialist units in India, and 25 healthy controls, provided fingerstick blood samples for the test. Spleen aspirates were taken from 250 patients. Kala-azar was confirmed by microscopy of spleen-aspirate smears in 127 patients. The K39 strip test was positive in all 127; the estimated sensitivity was therefore 100% (95% CI 98-100). Four patients had positive strip tests but negative aspirate smears; all four responded to treatment for leishmaniasis. 217 individuals, including the 25 healthy controls, 73 patients with malaria or tuberculosis, and 119 spleen-aspirate-negative patients who had presumed malaria or cirrhosis (79) or no final diagnosis (40), had negative strip-test results. None of the 119 aspirate-negative patients developed evidence of kala-azar during 3-6 months of follow-up. The estimated specificity of the strip test was 98% (95-100; 217/221). Detection of anti-K39 by immunochromatographic strip testing is a rapid and non-invasive method of diagnosing kala-azar, which has good sensitivity and specificity and is well suited for use in field conditions.

Urinary trypsinogen-2 test strip for acute pancreatitis

SummaryBackground A simple, rapid test that is specific and sensitive enough to distinguish, in patients with clinically suspected acute pancreatitis, those whose abdominal pain is indeed of pancreatic origin has proved elusive.Methods In two consecutive series of surgical patients in a teaching hospital, whose acute abdominal pain turned out to be due to acute pancreatitis (n=57) or extrapancreatic in origin (n=40), we studied urinary trypsinogen-2 in two ways. A test strip, incorporating monoclonal antibodies to two epitopes on trypsinogen-2, recorded a blue line when concentrations exceeded 50 μg/L; we also measured trypsinogen-2 concentrations in the laboratory.Findings In the patients with acute pancreatitis the test strip was positive in 52 and negative in five, whereas in the 40 extrapancreatic controls there were four false positives. In a further set of 57 orthopaedic controls, one urine was strip-test positive. Concentrations of urinary trypsinogen-2 and the test-strip results were in good agreement and in only three of the 154 patients were the two approaches discrepant, at the 50 μg/L cut-off.Interpretation These findings, in patients whose acute abdominal pain was known to be pancreatic in origin or not, are encouraging but need to be confirmed in a consecutive series of patients in whom the diagnosis of pancreatitis is in doubt.

Rapid Immunoassay for the Detection of Genital Herpes Infection

Objective: We evaluated a new affinity membrane strip test for the diagnosis of herpetic genital infections. Test strip results, which are available by immunoassay in 30 min without the need for special equipment, were compared with the results of viral culture. Methods: Twenty-eight female patients with vulvar lesions thought to be due to genital herpes simplex virus (HSV) infection were tested. The affinity membrane strip was applied to the genital lesion. Dacron swabs were then applied to the lesions and the swab contents cultured for HSV. For the immunoassay, the test strip was immersed in peroxidase-labeled antibodies specific for HSV type 2 (HSV-2), incubated, washed, and developed in the substrate tetramethylbenzidine. Positive reactions appeared as intense blue spots roughly the shape and size of the lesion. Sensitivity and specificity of the test were determined using the results of viral cultures as the standard. Results:The lesions of 8 patients yielded positive strips that correlated with positive cultures. The lesions of 6 patients produced positive strips but the cultures were negative. None of the patients whose lesions yielded negative strips had positive cultures. The lesions of 14 patients produced negative strips and negative cultures. Strips and viral cultures from 10 control patients (no lesions) were negative. Sensitivity and specificity were 100% and 70%, respectively. Positive (PPV) and negative (NPV) predictive values were 57% and 100%, respectively. The accuracy was 78%. Conclusions: The affinity membrane test was extremely sensitive in detecting herpetic genital infection compared with viral culture. The specificity was lower, resulting from false positives based on negative cultures. However, negative cultures may occur in the presence of disease, depending in part on the type of lesion. Thus, specificity may be higher than this preliminary study indicates, and more elaborate search for virus including serologic studies as well as larger groups of patients may be needed to refine this evaluation. With further testing and development, this membrane affinity test for herpes may yield a valuable adjunct to clinical diagnosis of this infection.

False-positive ketone tests: a bedside measure of urinary mesna

The sulfhydryl mesna is increasingly used to protect the bladder and kidney from effects of chemotherapy with ifosfamide and cyclophosphamide. Mesna reacts with reagents on urinary test strips designed to detect ketones. Test-strip results were correlated to sulfhydryl concentrations in 931 urine specimens obtained after infusions of mesna. These data may be used to estimate urinary mesna concentrations at the bedside or to test compliance in outpatients given oral mesna therapy.

Implications of probability analysis for interpreting results of leukocyte esterase and nitrite test strips.

We examined 288 urine samples, using test strips, sediment microscopy, and culture. The ability of the leukocyte esterase and nitrite test strips to detect or exclude urinary tract infection, as defined by a positive culture, was evaluated by probability analysis. We found that the diagnostic efficiency of the esterase-nitrite combination was similar to that of sediment microscopy. Moreover, once the strip test results had been obtained, little additional information was given by microscopy. The importance of estimating the prevalence, or pre-test probability, of infection before the test result is evaluated is emphasized. We conclude that, for detecting or excluding urinary-tract infection, microscopy can be replaced by the esterase and nitrite test strips. If the probability of infection predicted by the test strips is not high (or low) enough compared with medical decision limits, the samples should be cultured.

Evaluation of a rapid theophylline test strip assay in the emergency department setting.

Test strips recently have become available to measure theophylline levels. One such test strip (AccuLevel) had not been tested in an actual clinical situation with nontechnician personnel. We prospectively evaluated the test strip on consecutive emergency department patients, comparing it with the agglutination inhibition method used by our hospital laboratory. Nurses and medics who ran the test were given only a brief demonstration and explanation of the manufacturer's instructions. The 61 test strip levels correlated highly with the laboratory results (r = 0.92, slope = 0.89, y-intercept = 0.99). The test strip results were available in less time (mean of 0.51 hours vs 1.89 hours for the laboratory, P less than .0001). The most accurate readings were obtained by those who ran the test most frequently. Caffeine intake did not influence the test. Cost was significantly lower than charges at local hospitals.

Determination of a dynamic model for urethane prosthetic compounds

A frequency-response testing technique for determining the dynamic behavior of urethane prosthetic compounds is discussed. Experimental preparation of strip specimens and test results are presented. Sinusoidal response data of the tested strips are compared with three computer synthesizers (viscoelastic, viscous and complex modulus) of the one-dimensional wave equation for deciding on a model which best represents the material and subsequently calculating the value of a dynamic loss factor. The closed form solutions for the three mathematical models subject to sinusoidal boundary conditions are expressed in terms of functions which can be easily programmed for machine computation in FORTRAN IV language involving complex arguments. Dynamicloss factors are required for experimental and finite-element studies of prosthetic left ventricle of animal and human hearts. For the test strips, the loss factor, δ, is found to be dependent on the frequency.f. The results presented show that a viscoelastic model with a frequency-dependent loss factor of the form δ=c/f n is an excellent representation for analyzing the dynamic behavior of urethane compounds subjected to a range of frequencies corresponding to heart-beat rates. Derivation of the model parametersc andn is explained in detail.

Development of a Screening Test for L-Dopa and Its Metabolites in Urine

Abstract A simple screening test, sensitive to o-dihydroxyphenyl groups in the urine, was developed for use in monitoring patients with Parkinson's disease who are treated with L-dopa. Compounds measured by this test include dopa, dopamine, 3,4-dihydroxyphenylacetic acid, epinephrine, and norepinephrine. Parallel quantitative experiments, in which ion-exchange chromatography was used, followed by fluorometry and colorimetry, establish the validity of the strip-test results. The test is designed to be used by physician or patient, as well as by clinical laboratory personnel.