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Multi-centre evaluation of the urine test strip analyser Rapimat.

A multi-centre evaluation of the test strip analyser, Rapimat, was performed by four laboratories following the ECCLS 2nd draft guidelines for the evaluation of analysers in clinical chemistry. Using the Rapignost urine test strip with the test fields for bilirubin, urobilinogen, acetoacetate, ascorbic acid, glucose, protein, nitrite, pH and haemoglobin, the Rapimat was found to be analytically reliable in comparison with other, in most cases quantitative procedures. During the observation period of about 6 months no breakdown occurred in any laboratory. Interferences and sensitivity as discussed for the bilirubin and urobilinogen test field are more related to the test strip than to the instrument. Several improvements for further developments are suggested. This multi-centre study has shown that the ECCLS protocol is applicable to analytical procedures leading to discrete results.

Chemistry, Clinical↗

Hepatitis C virus antibodies in patients with chronic liver disease: ELISA and RIBA HCV strip immunoblot assay results.

In a study using the current first generation Ortho ELISA, a second generation Ortho ELISA, and the RIBA HCV strip immunoblot assay, all patients who were strongly positive for antihepatitis C virus (HCV) on ELISAs (OD490 > 3) were reactive to RIBA for multiple bands. While all ELISA false positive samples had low or intermediate OD490 values, RIBA confirmed HCV reactivity in 50% of the patients reactive to ELISA with a low suspicion of HCV infection, thus suggesting that RIBA HCV strip immunoblot assay will be most useful for patients who react weakly positive or intermediate to ELISA.

Chronic Disease↗

[Self-monitoring by patients with type-2 diabetes mellitus one year after initiation: user errors in a quarter of cases].

OBJECTIVE: To inventory the errors made during self-monitoring of blood-glucose values by diabetes patients. DESIGN: Descriptive. METHOD: In patients with type-2 diabetes mellitus who were registered with the West-Friesland Diabetes Care System (the Netherlands) during the period 1 April 2000-30 April 2001, and who had been monitoring their own glucose values for more than one year, checks for meter and user errors were carried out. When the patients first started using the glucose meter they were instructed by a diabetes nurse. The checks were carried out by a specially-trained nurse using a specifically-designed check list. RESULTS: Of the 249 participating patients, 123 were female and the mean age was 69 years. User errors in self-monitoring of the blood glucose occurred in 59 patients (24%). These primarily involved the use of expired or incorrect glucose strips (n = 17) and incorrect serial numbers (n = 16). No errors were made while placing the drop of blood on the glucose strip. Almost all patients had questions about the use of the glucose meter. CONCLUSION: Systematic checks of patient self-monitoring detected user errors in 24%.

Aged↗

Inconsistencies in the absorptive capacities of Schirmer tear test strips.

The absorptive capacities of 4 commercially available tear test strips were determined and compared with 5-mm X 40-mm strips of #41 filter paper. Significant differences in the absorption of water over a given time interval were found in 3 of the groups tested. Major inconsistencies were found only within 1 lot of tear test strips from a single manufacturer. Tear test strips from this lot consisted of 2 distinct populations that were distinguishable by transillumination. Strips with widely spaced horizontal lines had the same absorptive capacity as the filter paper, whereas those with fine lines consistently absorbed less water. The clinical importance of this discrepancy was verified by comparing measurements of tear production in 6 normal dogs.

Absorption↗

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.

Blood Glucose↗

Serological diagnosis of Indian visceral leishmaniasis: direct agglutination test versus rK39 strip test.

We evaluated the direct agglutination test (DAT), using freeze-dried (FD) and aqueous (AQ) antigen, and the rK39 immunochromatographic strip test in the diagnosis of Indian visceral leishmaniasis (VL). Sera from 508 subjects (150 parasitologically confirmed patients with VL, 100 and 153 healthy controls drawn from non-endemic and endemic regions, respectively, and 105 patients with other diseases presenting with fever and/or splenomegaly) were tested. The sensitivity of the tests were as follows: DAT (FD), 96% (95% CI 91-98); DAT (AQ), 97% (95% CI 93-99); rK39 strip test, 99% (95% CI 95-100). The specificity of DAT (FD), DAT (AQ) and rK39 strip tests were 85% (95% CI 81-88), 87% (95% CI 83-91) and 89% (95% CI 86-92), respectively. A significant correlation (high degree of agreement) was observed between all tests (kappa>0.80). We conclude that the sensitivity of FD antigen is comparable to that of AQ antigen. Similarly, the rK39 strip test is as sensitive as the DAT, but the strip test's greater convenience of use makes it a better tool for diagnosis of VL in peripheral areas of endemic regions.

Agglutination Tests↗

A simple and inexpensive screening test for low protein levels in urine.

Nigrosin binds to proteins yielding a dark blue complex. This reaction is used for detecting low protein concentrations in urine by applying spots of urine to cellulose acetate strips which are coloured by nigrosin. The intensity of coloured spots remaining after washing of the strips indicates protein concentration. With a cut-off at 50 mg protein/l, the test offers an excellent possibility for first line screening for microalbuminuria at lowest cost.

Albuminuria↗

Evaluating the validity of blood glucose monitoring strip interpretation by experienced users.

This study examined interpretations of blood glucose monitoring strips (BGMS) by patients and registered nurses (RNs) experienced in strip use. Visual interpretations of whole and bisected BGMS were compared with readings obtained with a reflectance meter. For whole strips, statistically significant differences were found when mean values of patient interpretations were compared with two of the three RNs and the meter. A significant difference was found between the average meter values and those for a third RN. When bisected strips were interpreted, a significant interaction effect was found between reader and strip condition. The RNs systematically underestimated bisected strips when compared with whole strips, whereas patients consistently underestimated both whole and bisected strips. The findings support the need for development of quality assurance monitors to evaluate users of patient self-care technologies such as BGMS.

Analysis of Variance↗

Test strip detection of Wuchereria bancrofti amplified DNA in wild-caught Culex pipiens and estimation of infection rate by a PoolScreen algorithm.

Bancroftian filariasis is targeted for elimination in the Nile Delta of Egypt. Improved simple methods are needed for monitoring Wuchereria bancrofti infection in the mosquito vector and thereby the success of elimination programmes. We evaluated the performance of the SspI-PCR assay combined with a DNA Detection Test StripTM method and used the PoolScreen algorithm method for estimating mosquito infection rates. A total of 769 indoor-resting Culex pipiens were captured in 79 randomly selected houses from a filaria-endemic village in the Nile Delta of Egypt (24.4% antigenaemia and 8.6% microfilaraemia). Collected mosquitoes were pooled by house, and assayed by the SspI-PCR. Amplified parasite DNA was detected by both electrophoresis of agarose gel stained with ethidium bromide (EtBr) and by test strips. PCR based on EtBr and test strip methods identified 43 (54.4%) and 45 (56.9%) houses, respectively, as being filaria positive. The minimum mosquito infection rate, assuming one infected female/pool was 6.85% by the PCR test strips. Mosquito infection rate calculated by the PoolScreen2 algorithm software amounted to 8.1% [95% confidence interval 5.85, 10.47]. Because it is faster and safer, the PCR test strip is a practical tool, especially when combined with the PoolScreen algorithm method, for xenomonitoring the success of elimination programmes.

Algorithms↗

Comparison of the techniques of evaluation of urine dilution/concentration in the dog.

The objective of this study was to evaluate the quality of the measurement of dog urine dilution/concentration by comparing osmolality with three methods of specific gravity (USG) measurement, i.e. weighing, refractometry and test strips. In unselected urine samples from 182 dogs there was a better agreement between osmolality and USG determination by refractometry (r = 0.92) than by weighing (r = 0.82) or by test strips (r = 0.27). There was an almost linear relationship between osmolality and USG: osmolality (mOsm/kg) = 36646(34318/38974) x (USGref - 1) + 25(-39/88); calculated osmolality differed from measured osmolality by more than 500 mOsm/kg in only 8 of 181 samples. There was a good agreement between USG determination by weighing and refractometry: USGref = 1.000(0.905/1.095) x USGweighing - 0.0004(-0.0019/0.0027), with a moderate bias. Only 12% of the differences between the two methods exceeded 0.010. Test strip assessment of USG was unreliable because of systematic underestimation and should not be used for dog urine. Refractometry is the best technique for routine evaluation of urine concentration/dilution when osmometry is not available.

Animals↗

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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Adolescent↗

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 40 nm 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 X 10(7) to 1.8 CFU/ml in enriched raw beef. E. coli O157 could be detected at a minimum of 1.8 x 10(5) 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.

Animals↗

Evaluation of the immunochromatographic CORIS Giardia-Strip test for rapid diagnosis of Giardia lamblia.

The aim of this study was to evaluate the performance of the CORIS Giardia-Strip test (CORIS Bioconcept, Gembloux, Belgium) as a rapid initial method for the routine diagnosis of giardiasis. Compared to a commercial ELISA-coproantigen test (ProSpect Giardia-ELISA-microplate assay; Remel, Lenexa, KS, USA), the commercial strip test had a sensitivity of 58%, a specificity of 99%, a positive predictive value of 93% and a negative predictive value of 93% (n=158). These results are comparable to those obtained using microscopy of direct wet-mounted stool. Since the CORIS Giardia-Strip test is simpler to perform, it can replace direct wet-mounted stool microscopy for the rapid diagnosis of giardiasis; however, its sensitivity is inferior to that of other immunochromatographic antigen detection tests and fresh stool samples are required for its use. Nevertheless, the results suggest that a positive CORIS Giardia-Strip test outcome does not need confirmation, while samples with negative results should be re-examined using another, more sensitive, test.

Animals↗

Screening for bacteriuria with the LN strip test.

Recently, the LN strip test was introduced for purposes of rapid screening of urine specimens for bacteriuria. The LN strip test permits detection of urinary leukocyte esterase and nitrite. A total of 2,481 unselected urine specimens from three tertiary care hospitals were examined using the LN strip test and the results were compared with those obtained with a conventional quantitative culture technique. When the results of the leukocyte esterase and nitrite tests were combined, the sensitivity and specificity of the LN strip test were 88.8% and 71.3%, respectively, based on culture results of greater than or equal to 10(5) CFU/ml. Test sensitivity decreased at greater than or equal to 10(4) CFU/ml, whereas test specificity increased.

Bacteriuria↗

Performance of the new plasma-compatible Advantage blood glucose test strips.

OBJECTIVE: To establish a plasma calibration curve for the Advantage Blood Glucose System that would permit direct comparison with results provided by clinical laboratories. DESIGN AND METHODS: The initial study involved the comparison between the Advantage whole blood referenced results and the laboratory plasma results. The second study validated the plasma-compatibility of the first new lot of Advantage test strips with this new calibration curve. RESULTS: Plasma and whole blood glucose data, obtained at Hôpital Maisonneuve-Rosemont in Montréal, demonstrated the typical differences between these two sample types. Mathematical correction of the Advantage results eliminated this difference. This new equation was then encoded into the code keys of a new lot of Advantage test strips and a second study was conducted to verify the comparability to laboratory plasma glucose. CONCLUSION: The results for the Advantage Blood Glucose System may now be compared directly with the laboratory plasma or serum glucose results.

Blood Chemical Analysis↗

Evaluation of Chemstrip LN in a male geriatric population.

A dipstick method for bacteriologic screening of urine using a combination of leukocyte esterase and nitrite indicators, Chemstrip LN, was evaluated in a male inpatient geriatric population. Three hundred seventy-five urine samples from 198 symptomatic patients (age range, 45 to 98 years; mean, 69.6) were tested by LN and cultured using standard methods. LN showed 169 negatives, but in 7 of these cases, the culture was positive (greater than or equal to 5 X 10(4) col/mL). Organisms recovered from these cultures were Candida (not albicans), Group B Streptococcus, Staphylococcus aureus, and in four cases, Pseudomonas aeruginosa. In the four cases of missed Pseudomonas the patients were receiving aminoglycoside therapy for 2 to 6 days and/or drugs that dye the urine. Despite the fact that many patients were on medications known to interfere with the test strips, the negative predictive value was still 96.0% showing that the strips may be suitable for use with this population given the understanding that certain antibiotics and/or substances that dye the urine may give false negative results.

Age Factors↗

Comparison of the RSV respi-strip with direct fluorescent-antigen detection for diagnosis of respiratory syncytial virus infection in pediatric patients.

The RSV Respi-Strip was compared to the SimulFluor respiratory screen for detecting respiratory syncytial virus in nasopharyngeal aspirates from pediatric patients. Of samples tested, 115/239 (49%) were positive by direct fluorescent-antigen detection. The sensitivity and specificity of the RSV Respi-Strip were 92% (95% confidence interval [CI], 86% to 96%) and 98% (95% CI, 94% to 100%), respectively, with a diagnostic efficiency of 95%.

Adolescent↗

Automation of urine sediment examination: a comparison of the Sysmex UF-100 automated flow cytometer with routine manual diagnosis (microscopy, test strips, and bacterial culture).

Urine specimens from 438 patients were examined with the UF-100 flow cytometer (Sysmex TOA Medical Electronics (Europe) GmbH, Hamburg, Germany) and by manual microscopy and test strips. One hundred and forty-two of these were also examined bacteriologically. The measurements with the UF-100 were performed on native urine without prior centrifugation. Intraassay imprecision, CV of 1.3% (547/microliter) to 8.5% (24/microliter) for erythrocytes and CV of 2.4% (218/microliter) to 5.6% (10/microliter) for leukocytes, are similar to those usual in clinical chemistry, and are very much better than those seen in manual microscopy of sediment. In routine use, overloading the flow cytometer by an excessive concentration of particles was observed in 9% of specimens. Such specimens should be checked visually. The UF-100 is distinctly more sensitive than manual microscopy for determining leukocytes, erythrocytes, epithelial cells and bacteria. Reference ranges were estimated from the results obtained. These enabled the UF-100 to replace routine manual diagnostic methods. Although the sensitivity is improved over manual microscopy of sediment, it is always necessary to perform parallel test strip examination when determining erythrocytes in order to detect haemolysis. In our opinion the Sysmex UF-100 is a suitable replacement for manual microscopy of urine sediment. In addition it offers an opportunity to improve standardization of basic urinalysis.

Automation↗