Test Strip Reading Research Articles

Visualization test strip reading of urine miRNA via cascade selective recognition reactions for non-invasive diagnosis of bladder cancer

This study proposed a homogeneous enzyme-free and nucleic acid-based catalytic hairpin assembly and cascade recognition reactions strategy that used calcein as the signal reporter for dual visualization (color and length) and fluorescence signal detection of bladder cancer marker miRNA-126 in clinical urine. This strategy was based on the ability of calcein and CuS nanoparticles (NPs) to recognize C-Ag+-C structure/Ag+/Cu2+/CuS NPs and C-Ag+-C structure/Ag+, respectively. Due to the integration of cascade amplification and material cation exchange reaction (CER), the sensitivity of homogeneous enzyme-free miRNA analysis at room temperature was significantly improved. This study achieved the limits of detections (LODs) as low as 0.25 aM of miRNA-126 and single-cell level of T24 cells with fluorescence mode. And the reading mode of color and length changes could detect miRNA and cells with concentrations as low as 5 aM and 1 cell/mL without instruments, respectively. And less reduction of fluorescence signal was observed when target miRNA was replaced with these base-mismatched RNAs. Then miRNA-126 in 66 clinical urine samples was quantified. The experimental results were consistent with the polymerase chain reaction (PCR) kit, computed tomography (CT), and pathological findings. The receiver operating characteristic (ROC) curve exhibited an area under the curve (AUC) value of 0.954, and the assay showed 100% specificity and 90% sensitivity.

Diagnostic Accuracy for Periprosthetic Joint Infection Does Not Improve by a Combined Use of Glucose and Leukocyte Esterase Strip Reading as Diagnostic Parameters.

The diagnosis of periprosthetic infections (PJI) can be challenging in clinical practice because the clinical presentations of aseptic loosening and low-grade infections are similar. Semiquantitative evaluation of leukocyte esterase (LE) in synovial fluid using a urine strip test has already established itself as a diagnostic method over the past decade. The analysis of LE in synovial fluid leads to a high number of false-positive test results. In the present study, the value of a combined semiquantitative determination of glucose and LE in synovial fluid to improve the diagnosis of PJI was investigated. Over a 4-year period, 145 synovial samples were collected from patients who developed joint effusion after arthroplasty. LE and glucose test strips were considered as an index test for the diagnosis of PJI. A ++ or +++ LE and a negative glucose test strip reading were considered as positive test results. Modified diagnostic criteria for PJI as recommended by the Musculoskeletal Infection Society (MSIS) served as the reference test, except that intraoperative findings were excluded. Forty-six out of 145 samples were classified as septic complication according to the reference test. In regard to PJI, our data showed that combined use of LE and glucose strip test reading displayed a 98.0% specificity (95% confidence interval (CI): 95.2% to 100%), a 50% sensitivity (95% CI: 35.6% to 64.4%), a 92% positive predictive value (95% CI: 81.4% to 100.0%), and an 80.3% negative predictive value (95% CI: 73.2% to 87.4%). In contrast, the exclusive analysis of LE on the urine strip to diagnose PJI demonstrated a 90.9% specificity (95% CI: 85.2% to 96.6%), a 67.4% sensitivity (95% CI: 53.8% to 80.9%), a 77.5% positive predictive value (95% CI: 64.6% to 90.4%), and an 85.7% negative predictive value (5% CI: 79.0% to 92.4%). A combination of LE and glucose test pad reading is considered superior as a potential “rule-in” method for the diagnosis of PJI compared with LE test pad analysis alone. However, combined LE and glucose synovial fluid testing also demonstrated lower test sensitivity and thus diagnostic accuracy compared with LE analysis alone. Therefore, combined glucose and LE test pad analysis does not represent a sufficient diagnostic standard to exclude PJI with certainty.

A saliva urea test strip for use in feline and canine patients: a pilot study.

We evaluated a saliva urea test strip (Kidney-Chek; SN Biomedical), as a rapid, noninvasive method to screen for azotemia. The test is a semiquantitative method that assesses 7 levels of saliva urea concentration, and indirectly serum urea, from <3 to >17 mmol/L. Ninety-two dogs (14 azotemic) with serum urea of 1.3–37 mmol/L and 56 cats (16 azotemic) with serum urea of 4.1–89.3 mmol/L were enrolled. A positive correlation was found for saliva urea against serum urea in each species (dogs: rs = 0.30, p < 0.005; cats: rs = 0.50, p < 0.001). After turning the semiquantitative data into continuous data by attributing to each level the midpoint of the described range, a receiver operating characteristic curve analysis showed good performance for detecting serum urea above the upper limit of the laboratory RI (dogs: 2.1–11.1 mmol/L; cats: 5–12.9 mmol/L), with an area under the curve of 0.81 in dogs and 0.83 in cats. We recommend that the test be used as an exclusion test, given that it cannot confidently confirm azotemia with higher test results. Additional investigations are recommended for dogs with a test strip reading of ≥9–11 mmol/L and for cats with a test strip reading of ≥12–14 mmol/L.

The effect of adjusting the stroke value of jet dispenser on the performance of glucose biosensor with gold-plated electrode.

This study investigates the effect of dispensing glucose oxidase enzyme onto the reaction zone of a golden electrode via a jetting dispenser. Each droplet of enzyme solution dispensed onto the reaction zone of golden electrode weighs exactly the same at around 0.4 mg. This study shows that the spring and needle assembly can be controlled by adjusting the stroke value of the stroke adjustment knob to generate different jet dispensing effects, thus affecting the change of droplets of glucose oxidase enzyme solution within the reaction zone of the golden electrode. This study performs experiments using three stroke values, which are 0.8, 1.2, and 1.6 mm. The experimental results show that adjusting the stroke value to change the droplet of the dispensing liquid will significantly affect the accuracy of the test strip reading value. When the stroke value is adjusted to 1.5 mm, the standard deviation of the test strip is 3.8 mg/dL and the coefficient of variation is 4.1%-6.1%. The study suggested that adjusting the stroke value can stabilize the dispensed droplet to increase the stability of test strip reading, improving the accuracy of the test strip reading. This adjustment method can also be applied to the process of other biochemical sensors.

Quantitative urine test strip reading for leukocyte esterase and hemoglobin peroxidase

Recently, urine test strip readers have become available for automated test strip analysis. We explored the possibilities of the Sysmex UC-3500 automated urine chemistry analyzer based on complementary metal oxide semiconductor (CMOS) sensor technology with regard to accuracy of leukocyte esterase and hemoglobin peroxidase results. We studied the influence of possible confounders on these measurements. Reflectance data of leukocyte esterase and hemoglobin peroxidase were measured using CMOS technology on the Sysmex UC-3500 automated urine chemistry analyzer. Analytical performance (imprecision, LOQ) as well as the correlation with white blood cell (WBC) and red blood cell (RBC) counts (Sysmex UF-5000) were studied. Furthermore, the influence of urinary dilution, haptoglobin, pH and ascorbic acid as confounders was determined. Within- and between-run imprecision (reflectance signal) ranged from 1.1% to 3.6% and 0.9% to 4.2% for peroxidase and 0.4% to 2.5% and 0.4% to 3.3% for leukocyte esterase. Good agreement was obtained between the UF-5000 for RBCs and peroxidase reflectance (r=0.843) and for WBCs and leukocyte esterase (r=0.821). Specific esterase activity decreased for WBC counts exceeding 100 cells/μL. Haptoglobin influenced the peroxidase activity, whereas leukocyte esterase and peroxidase activities showed a pH optimum between 5.0 and 6.5. A sigmoidal correlation was observed between urinary osmolality and peroxidase activity. CMOS technology allows to obtain high quality test strip results for assessing WBC and RBC in urine. Quantitative peroxidase and leukocyte esterase are complementary with flow cytometry and have an added value in urinalysis, which may form a basis for expert system development.

Limits of preservation of samples for urine strip tests and particle counting

Preservation of urine samples is important for centralised laboratory services with automated instruments. A multicentre evaluation was carried out to assess preservative tubes from BD Diagnostics-Preanalytical Systems and from Greiner Bio-One for test strip reading (documented at the level of remission values), for particle counting by flow cytometers (UF-100) and for visual microscopy. Failures were expressed as percentages of originally positive samples beyond a two-fold change (+100% or -50%) from the original values. The preservative-containing BD Plus C&S plastic, BD Plus UAP and Greiner Stabilur tubes succeeded in preservation of test strip results for 6-24 h (exceptions were glucose and nitrite tests). Greiner boric acid tube showed false negative results in leukocyte, protein and ketone strip tests immediately after adding the preservative. Urine red blood cell counts (with Sysmex UF-100) were preserved for 5 h in BD Plus C&S plastic and Greiner Stabilur tubes (Greiner tubes having clearly larger preservative-related background). Bacteria or white blood cell counting succeeded in BD Plus C&S plastic tubes for 5 or 24 h, respectively, but up to 72 h in Greiner Stabilur tubes. In visual microscopy, the Greiner Stabilur tube was slightly better than the BD Plus C&S plastic tube. Urine specimens can be transported at +20 degrees C on the day of collection if preserved properly. Longer delays need careful planning with current preservatives. Flow cytometry with UF-100 is sensitive to non-dissolved preservative remnants.

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.

Assessment of nicotine uptake from cigarette smoke: comparison of a colorimetric test strip (NicCheck I™) and gas chromatography/mass selective detector

Colorimetric test strip assays are a convenient and inexpensive means for the determination of cotinine in human urine because they can be performed in a nonlaboratory environment using a trained technician. Four hundred human urine samples were separated into four categories: (1) heavy smokers (>20 cigarettes smoked per day), (2) light smokers (<20 cigarettes smoked per day), (3) non-smokers, and (4) vegetarian non-smokers. Samples were evaluated by a gas chromatography/mass selective detector (GC/MSD) method as a reference and using NicCheck I™ (DynaGen, Inc.). Colour intensity can range from 0 (no colour) to 14 (deep pink). Qualitative values were assigned as negative (0), low (1-6) and high (7-14). Comparison of the test strip and GC/MSD results showed: (1) 43 (10.75%) false negatives using the criterion of a GC/MSD cotinine level above 200 ng ml-1 and test strip reading of 0, (2) 31 (7.75%) false positives using the criterion of a GC/MSD cotinine level below 1 ng ml-1 and a test strip reading of 1 or greater, and (3) no correlation between the test strip and GC/MSD results (r = 0.597, p < 0.05). The fact that the colorimetric reaction is sensitive to many nicotine metabolites and/or heterocyclic amine structures whereas the GC/MSD method measures nicotine and cotinine selectively might explain the false positive results. False negative results were likely to be due to a lack of sensitivity of the test strip.

Colorimetric strip tests: a comparison of visual and reflectometric measurements for quantitative applications

The use of indicator-based colorimetric strip tests for measuring chromate and nitrate in spiked and waste water samples was validated. Test strip readings made by reflectometry were significantly more accurate and reproducible than those made by a visual comparisons to a reference color chart. Each of the analytes was consistently detected at 1 to 2 μg/ml, using the reflectometer. There was an excellent correlation between the analytical results obtained with the strip tests and those obtained using the more traditional laboratory methods of inductively coupled plasma/mass spectrometry and ion chromatography. This study shows that the use of strip tests for field screening, and as a prescreen in the laboratory, can be a time- and cost-effective alternative or adjunct to currently used laboratory methods.

The Frequency of Hypoglycemia in Full-Term Large and Small for Gestational Age Newborns

Although various authors recommend screening for hypoglycemia in large for gestational age (LGA) and small for gestational age (SGA) newborns, the frequency of hypoglycemia in these infants, using a recent definition of hypoglycemia, and the proper duration of screening are not documented. We determined chromogen test strip blood glucose values at ages 1, 2, 3, 6, 12, 24, 36, and 48 hours in full-term LGA and SGA infants whose mothers were not diabetic. Serum glucose determination was immediately done if a test strip reading was less than 40 mg/dl. Hypoglycemia was defined as a serum glucose less than 35 mg/dl at less than 3 hours of age, less than 40 mg/dl at 3 to 24 hours of age, and less than 45 mg/dl at more than 24 hours of age. The frequency of hypoglycemia in LGA infants was 8.1% (95% confidence interval [CI] 5.0 to 11.2%), and in SGA infants, 14.7% (95% CI 9.8 to 19.6%). The mean age at which hypoglycemia occurred was 2.9 hours (range, 0.8 to 8.5) in LGA infants, and 6.1 hours (range, 0.8 to 34.2) in SGA infants. There were no differences in other possible risk factors between the hypoglycemic and euglycemic infants except that in SGA infants meconium-stained amniotic fluid (40% vs 20%, p = .001), maternal preeclampsia (27% vs 8%, p = 0.0056), and male sex (29% vs 9%, p = 0.029) were more common in hypoglycemic than in euglycemic infants. These data suggest that screening for hypoglycemia in LGA infants whose mothers are not diabetic may be stopped after 12 hours, but should continue for 48 hours in SGA infants.

A prospective evaluation of glucose reagent teststrips in the prehospital setting

Reagent teststrip determination of blood glucose has been shown to be accurate for hospital and home testing and is commonly used in prehospital care despite the lack of studies in this arena. This prospective, multicenter study examines the ability of glucose reagent teststrips to detect hypoglycemia when used under field conditions compared with simultaneously drawn control samples for laboratory glucose determination. Also examined was the accuracy of the teststrips in the laboratory glucose range ≤200 mg/dL. One hundred eighty-one pairs of data were analyzed. Hypoglycemia was defined as laboratory glucose ≤60 mg/dL. The teststrips correctly identified 31 of 33 patients in this range (sensitivity = 94%), and 125 of 148 patients without hypoglycemia (specificity = 85%). The two false negative readings were 70 and 90 mg/dL. Reagent teststrips were within ±40 mg/dL of the laboratory value in 70% of cases. The correlation coefficient (Spearman r) between teststrip and laboratory glucose in the range ≤200 mg/dL was. 80. Using teststrip readings of 90 mg/dL or less as a measure of hypoglycemia yields 100% sensitivity with a specificity of 57%. We conclude glucose reagent teststrips are a useful adjunct for use in the prehospital setting and may be valuable for the detection of hypoglycemia.

A Comparison of Chromogen Test Strip (Chemstrip bG) and Serum Glucose Values in Newborns

Although glucose oxidase-peroxidase chromogen test strips are frequently used to estimate serum glucose values in newborns, previous studies have not evaluated multiobserver variability of test strip readings and have included few infants with hypoglycemia. We compared values of 272 samples of serum glucose with values simultaneously obtained by chromogen test strips (Chemstrip bG) in newborns. The diagnostic sensitivity of a chromogen test strip less than 2.2 mmol/L for predicting a serum glucose level less than 1.9 mmol/L was 86% (95% confidence interval [CI], 75% to 94%), with 78% specificity (95% CI, 73% to 84%). The positive predictive value in our specimens, with a 21% prevalence of serum glucose levels less than 1.9 mmol/L, was 52% (95% CI, 41% to 62%), with a negative predictive value of 95% (95% CI, 91% to 100%). Fifty-eight of our serum glucose values were less than 1.9 mmol/L and the levels obtained by chromogen test strip were greater than or equal to 2.2 mmol/L in 8 of these cases. Review of these 8 cases showed that a delay in performing the laboratory glucose oxidase serum glucose could account for the discrepancy in 2 cases. Chromogen test strips are readily available and easy to use, but more sensitive, specific, accurate, and precise methods of serum glucose screening in newborns are needed.

Less expensive, reliable blood glucose self-monitoring.

We examined the reliability of split test strips for blood glucose self-monitoring. One hundred visual readings were performed with each of the following test strips: original Haemoglukotest 20-800 (HGT 1/1; Boehringer-Mannheim, Mannheim, FRG) and Haemoglukotest 20-800 halved either by a splitting device (HGT 1/2 SP) or by a pair of scissors (HGT 1/2 SC). Within the plasma glucose range of 20-360 mg/dl, there was a close correlation between the results of all three test-strip readings and the values obtained by the reference method (Beckman glucose analyzer): HGT 1/1, r = .950; HGT 1/2 SP, r = .966; and HGT 1/2 SC, r = .966. Absolute deviations from the reference values were 17 +/- 2, 17 +/- 1, and 17 +/- 1 mg/dl (mean +/- SE). Analysis of variance did not reveal any significant differences between the values of each of the three procedures compared with the reference method (P = .98). These results indicate that visual reading of split test strips is as reliable as the reading of original test strips. A special splitting device is not necessary. Diabetic patients should be advised to use split test strips for blood glucose self-monitoring to reduce costs.

Further evaluation of the SG test strip for estimation of urinary osmolality.

The mass densities of 2000 urines from children and 2000 urines from adults were determined with the new test strip, Multistix SG, and the results were compared with osmolality measurements. Normal urinary parameters were investigated for possible interference with the test strip reading. Variations in the pH and ionic composition of urine considerably influenced the test strip reading, whereas nonionic compounds, such as glucose and urea, showed practically no interference. For patients on a normal diet and without metabolic diseases, the new test strip is more appropriate than urometry for the determination of the mass density of the urine.

Diagnostic value of a test-strip in detecting increased urinary excretion of albumin, IgG and β2-microglobulin in patients with suspected proteinuria

Hemmingsen, L. & Skaarup, P. Diagnostic value of a test-strip in detecting increased urinary excretion of albumin, IgG and β2-microglobulin in patients with suspected proteinuria. Scand. J. clin. Lab. Invest. 41, 785—789, 1981.Test-strip screening for increased urinary protein excretion was performed in 482 patients with suspected proteinuria. The test-strip readings were compared with the urinary concentration and 24-h excretion of albumin, IgG and β2-micro-globulin (β2m), determined by an immunoprecipitin reaction, using the upper limit of the reference interval for these proteins for descriminating between normal and increased protein excretion. Increased concentration and 24-h excretion of albumin and IgG showed about 25 and 40 % false negative text-strip reactions, respectively, whereas only few false positive reactions were observed. Thus the predictive value of a negative test was low and that of a positive test high. The overall predictive value in detecting increased urinary excretion of β2m was ...