Performance of the dipstick screening test as a predictor of negative urine culture / Desempenho da fita de urina como resultado presuntivo para cultura de urina negativa

ABSTRACT Objective To investigate whether the urine dipstick screening test can be used to predict urine culture results. Methods A retrospective study conducted between January and December 2014 based on data from 8,587 patients with a medical order for urine dipstick test, urine sediment analysis and urine culture. Sensitivity, specificity, positive and negative predictive values were determined and ROC curve analysis was performed. Results The percentage of positive cultures was 17.5%. Nitrite had 28% sensitivity and 99% specificity, with positive and negative predictive values of 89% and 87%, respectively. Leukocyte esterase had 79% sensitivity and 84% specificity, with positive and negative predictive values of 51% and 95%, respectively. The combination of positive nitrite or positive leukocyte esterase tests had 85% sensitivity and 84% specificity, with positive and negative predictive values of 53% and 96%, respectively. Positive urinary sediment (more than ten leukocytes per microliter) had 92% sensitivity and 71% specificity, with positive and negative predictive values of 40% and 98%, respectively. The combination of nitrite positive test and positive urinary sediment had 82% sensitivity and 99% specificity, with positive and negative predictive values of 91% and 98%, respectively. The combination of nitrite or leukocyte esterase positive tests and positive urinary sediment had the highest sensitivity (94%) and specificity (84%), with positive and negative predictive values of 58% and 99%, respectively. Based on ROC curve analysis, the best indicator of positive urine culture was the combination of positives leukocyte esterase or nitrite tests and positive urinary sediment, followed by positives leukocyte and nitrite tests, positive urinary sediment alone, positive leukocyte esterase test alone, positive nitrite test alone and finally association of positives nitrite and urinary sediment (AUC: 0.845, 0.844, 0.817, 0.814, 0.635 and 0.626, respectively). Conclusion A negative urine culture can be predicted by negative dipstick test results. Therefore, this test may be a reliable predictor of negative urine culture.

RESUMO Objetivo Verificar se a triagem de urina por fitas reativas é capaz de predizer a cultura de urina. Métodos Estudo retrospectivo realizado entre janeiro e dezembro de 2014 com 8.587 pacientes, com solicitação médica de triagem de urina (fita), sedimento urinário e cultura de urina. Foram analisados sensibilidade, especificidade, valor preditivo positivo, valor preditivo negativo e curva ROC. Resultados Foram positivas 17,5% das culturas. O nitrito apresentou sensibilidade de 28% e especificidade de 99%. O valor preditivo positivo foi de 89% e o valor preditivo negativo de 87%. Esterase apresentou sensibilidade de 79% e especificidade de 84%. Valor preditivo positivo e valor preditivo negativo foram de 51% e 95%, respectivamente. A combinação de nitrito ou esterase positivos apresentou sensibilidade de 85% e especificidade de 84%. Valor preditivo positivo e valor preditivo negativo foram, respectivamente, 53% e 96%. O sedimento positivo (mais de dez leucócitos por microlitro) apresentou sensibilidade de 92% e especificidade de 71%. O valor preditivo positivo foi 40% e o negativo, 98%. A combinação de nitrito e sedimento urinário positivos apresentou sensibilidade de 82% e especificidade de 99%. Os valores preditivos positivo e negativo foram 91% e 98%, respectivamente. Para o nitrito ou esterase positivos mais os leucócitos positivos, a sensibilidade foi de 94% e a especificidade de 84%. O valor preditivo positivo foi de 58% e o negativo foi de 99%. Com base na curva ROC, o melhor indicador de urocultura positiva foi a associação entre a esterase ou nitrito positivos na fita mais os leucócitos positivos no sedimento, seguido por nitrito e esterase positivos, sedimento urinário positivo isolado, esterase positiva isolada, nitrito positivo isolado e, finalmente, pela associação entre nitrito e sedimento urinário positivos (AUC: 0,845, 0,844, 0,817, 0,814, 0,635 e 0,626, respectivamente). Conclusão Uma urocultura negativa pode ser prevista com resultados negativos na fita. Portanto, este teste pode ser um preditor confiável de urocultura negativa.

Dipstick spot urine pH does not accurately represent 24 hour urine PH measured by an electrode

ABSTRACT Objectives To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode. Materials and Methods We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recent pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered an inaccurate result. Results A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588). Conclusions Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH.

Evaluación de un sistema automatizado de siembra de orinas para urocultivos / Evaluation of an automated streaking system of urine samples for urine cultures

Introduction: Automated systems have simplified laboratory workflow, improved standardization, traceability and diminished human errors and workload. Although microbiology laboratories have little automation, in recent years new tools for automating pre analytical steps have appeared. Objectives: To assess the performance of an automated streaking machine for urine cultures and its agreement with the conventional manual plating method for semi quantitative colony counts. Materials and Methods: 495 urine samples for urinary culture were inoculated in CPS® agar using our standard protocol and the PREVI™ Isola. Rates of positivity, negativity, polymicrobial growth, bacterial species, colony counts and re-isolation requirements were compared. Results: Agreement was achieved in 98.97% of the positive/negative results, in 99.39% of the polymicrobial growth, 99.76% of bacterial species isolated and in 98.56 % of colony counts. The need for re-isolation of colonies decreased from 12.1% to 1.1% using the automated system. Discussion: PREVI™ Isola's performance was as expected, time saving and improving bacterial isolation. It represents a helpful tool for laboratory automation.

Introducción: Los sistemas automatizados han facilitado el flujo de trabajo, mejorado la estandarización, la trazabilidad, disminuido el error humano y la carga de trabajo en los laboratorios. A pesar de que la microbiología ha permanecido poco automatizada, en los últimos años han aparecido nuevas herramientas para la automatización de la etapa pre analítica. Objetivos: Evaluar el desempeño de un sistema automatizado de siembra de urocultivos y la concordancia con la siembra manual convencional en el recuento semicuantitativo de colonias. Materiales y Métodos: 495 muestras de orinas fueron sembradas según nuestro protocolo habitual y comparadas con las placas de CPS® obtenidas con PREVI™ Isola en cuanto a positividad/negatividad, muestras polimicrobianas, especies de bacterias aisladas, recuentos y necesidad de resembrar. Resultados: Hubo concordancia en 98,97% de los positivos y negativos, en 99,39% de las muestras polimicrobianas, en 99,76% de las especies aisladas y en 98,56% de los recuentos. La necesidad de resiembra disminuyo de 12,1% a un 1,1% usando este sistema automatizado. Discusión: El desempeño de PREVI™ Isola fue el esperado, mejorando el aislamiento bacteriano y el tiempo requerido y representa una buena herramienta para la automatización de laboratorios.

Cost benefit of the routine urinalysis

In the present health care environment, cost-benefit analysis is extremely important. In this screening program, the minimal cost of screening dipstick urinalysis in 1601 asymptomatic school children was determined. The process of screening was similar to all the studies. The minimal cost utilizing 3 general physicians was calculated. Costs were determined by using current charge for supplies ordered to perform tests, charges for tests performed by a commercial laboratory, and the cost of a final evaluation by a pediatric nephrologist. Initial abnormal urinalysis was found in 4.7% [76/1601] of patients. Upon retesting 1.37% [22/1601] of patients were calculated to have a persistent abnormality. The calculated cost was 1/530/000 Rials [164.5 $] to initially screen all 1601 patients with a dipstick urinalysis or 850 Rials [0.09 $] per patient. The calculated cost to evaluate the 22 patients with any persistent abnormality on repeat dipstick urinalysis was 246/840 Rials [26.5 $] or 11.220 Rials [1.2 $] per patient. This is the calculated cost for a single screening of 1601 asymptomatic pediatric patients. Multiple screening dipstick urinalysis in asymptomatic pediatric are costly and should be discontinued. We purpose that a single screening dipstick urinalysis be obtained at school entry age, between 6 and 7 years old, in all asymptomatic children

Evaluation of iQ200 Automated Urine Microscopy Analyzer / 대한진단검사의학회지

BACKGROUND: Microscopic examination of urine sediment is one of the most commonly performed tests in the clinical laboratory. However, manual microscopic sediment examination is labor-intensive, time-consuming and imprecise. In this study, we evaluated the analytical performance and clinical usefulness of a recently introduced image-based automated urinalysis system, Iris iQ200 (Iris Diagnostics, USA). METHODS: We assessed the iQ200 for linearity, precision and carryover rate using patient's samples and quality control materials. On 337 urine samples, urine sediment analyses performed by the iQ200 were compared with manual microscopy results. RESULTS: The iQ200 showed a good linearity (r2>0.99) for all cellular components analyzed. Within-run and total CVs on urine specimens and quality control samples were less than 10% except for within-run CV for the samples with low concentration of the squamous epithelial cells. The carryover rates were 0.21% for RBCs and 1.92% for WBCs. The agreement rates within one grade between the iQ200 and manual microscopy for RBCs, WBCs, and squamous epithelial cells were 93.8%, 94.2% and 96.9%, respectively. CONCLUSIONS: Since the iQ200 showed a reliable analytical performance and good concordance with manual microscopy, it could be useful in the clinical practice as a screening procedure.

Infecção do trato urinário: urinocultura e avaliação de métodos / Urinary tract infection: urineculture and evaluation methods

Amostras de urina de 40 pacientes do Hospital Municipal Lourenço Jorge/RJ foram analisadas pelos métodos de: diluição, laminocultivo e alça calibrada. As bactérias encontradas foram identificadas em ágr Mac Conkey e pelos testes de citrato, motilidade, indol e sulfeto. Em 80 por cento dos resultados houve concordância quanto à interpretação do diagnóstico pelos três métodos. Nos 20 por cento restantes, a divergência não foi significativa em favor de qualquer método. Houve total concordância dos métodos de alça calibrada e de diluição quanto à identificação dos agentes. Porém, a concordância do laminocultivo foi de apenas 12,5 por cento e a adição do teste de motilidade a este método permitiu a distinção entre Klebsiella sp. e Enterobacter sp. Os pontos críticos de cada método devem ser conhecidos para que a escolha não resulte em falhas na identificação dos agentes.

Evaluation of the Sysmex UF-100 automated urinalysis analyzer and comparative study with JCCLS reference method.

Microscopic urine sediment analysis has been accepted as the mainstay test for examining urine cells and particles. Although it provides essential information for clinicians about disease states in the patients, it is a high-volume and laborious procedure. Therefore, an automated analyzer was developed recently and has just been introduced to Thailand. In this study, the authors evaluated the analytical performance of this new automated urine analyze. Also a comparative study was performed between the UF-100 test results and those of JCCLS reference method. In evaluation of the Sysmex UF-100 automated urinalysis analyzer, both precision and linearity studies were performed. Between-run CVs for RBCs (mean = 182.46/microl), WBCs (mean = 193.37/microl), ECs (mean = 70.05/microl) and casts (mean = 12.21/microl) were 7.74 per cent, 5.52 per cent, 21.32 per cent and 7.69 per cent, respectively. Concerning the within-run CVs for the RBC analysis, the CV ranged from 16.28 per cent for low numbers of RBCs (35.67/microl) to 2.93 per cent at RBC concentrations (712.13/microl). Concerning within-run precision for the WBC analysis, the CV ranged from 22.31 per cent for low numbers of WBCs (WBCs 12.53/microl) to 2.07 per cent at a WBC count of 211.01/microl. Within-run precision ranged from 11.36 per cent at 24.99 ECs/microl to 6.18 per cent at 53.08 ECs/microl. Within-run precision for casts varied from 35 per cent for samples with 1.33 casts/microl to 12.38 per cent for samples with 4927.35 casts/microl. From the comparative study, good agreements (p < 0.05) were obtained between UF-100 and JCCLS reference method for RBCs counts (p = 0.000, r = 0.974) and WBCs counts (p = 0.000, r = 0.913). However, fair agreement (p > 0.05) was obtained between UF-100 and JCCLS reference method for ECs counts (p = 0.017, r = 0.212) and casts counts (p = 0.624, r = 0.044). In conclusion, the UF-100 analyzer is a new useful analyzer although it cannot be a substitute for microscopic sediment examination.

Qual o valor da sedimentoscopia em urinas com características físico-químicas normais? / Is it worth-while doing urine sediment microscopy in dipstick physiocochemical normal samples?

O valor da sedimentoscopia em amostras de urina com exame físico-químico normal é questionado na literatura médica estrangeira, sendo que muitos pesquisadores a julgam desnecessária. Procurando contribuir para a elucidação desta dúvida e levando-se em conta que a maioria dos laboratórios brasileiros sempre executa o exame completo, foi analisada uma amostragem de uma clientela essencialmente ambulatorial, cujas requisições não permitiam determinar se havia finalidade diagnóstica. Fez-se um estudo de 10.234 amostras, que foram submetidas ao exame de rotina, sendo que 5.000 apresentaram exames físico-químicos normais. Destas foi feita uma avaliação dos achados da microscopia do sedimento que pudessem ser considerados possivelmente relevantes clinicamente. Entre esses achados, os de maior incidência foram: cilindros (29 exames - 0,58 por cento) e piócitos em número igual ou superior a cinco por campo (26 exames - 0,52 por cento). Todos os demais parâmetros foram encontrados em números iguais ou inferiores a 0,4 por cento. Um percentual de 98,02 por cento destas amostras não revelou anormalidade à microscopia. A análise estatística pelo método do X² (p < 0,01) sugere que não há necessidade da execução da sedimentoscopia nas urinas sem anormalidades no exame físico-químico, o que representaria uma redução de 48,85 por cento dos sedimentos examinados. Desta forma se obteria uma sensível economia de tempo e de gastos, sem nenhum prejuízo para o paciente

Semiquantitative determination of urinary glucose: comparison of home-made strip and routine tests.

Glucose oxidase paper strips for semiquantitative determination of glucose in urine are commercially available but details of their preparation are not published. The purpose of this study was to produce such strips, using a coupled enzyme glucose oxidase-peroxidase reaction which would yield purple color with ortho-tolidine, and safranin upon dipping into urine containing glucose. In this present study, without any special equipment, special humidity and temperature control, the new reagent strip named R-strip could be successfully prepared in the atmospheric conditions of Thailand. R-strips were evaluated against random urine added with various amounts of glucose in comparison with a commercial strip (T-strip), Benedict's test, and a commercial tablet (C-tablet), routinely used in laboratories. The developed strips were found to be as specific as T-strip and more sensitive than other tests.

Depuración de creatinina en pacientes geriátricos. Cálculo mediante fórmula de Cockcroft-Gault / Creatinine clearance in geriatric patients and its calcule by Cockcroft-Gault equation

El objetivo fue identificar la correlación entre la depuración creatinina en orina de 24 horas y la fórmula de Cockcroft-Gault en el pacientes geriátricos. En el Hospital General de Zona No.27 del Instituto Mexicano del Seguro Social se realizo un estudio descriptivo de 51 pacientes, de quienes se registró edad, sexo, peso, creatinina sérica y depuración de creatinina en orina de 24 horas. La edad media fue de 72 ñ 7 años; 51 por ciento perteneció al sexo femenino, 70.5 por ciento tuvo creatinina sérica normal y de éstos 39 por ciento presentó depuración de creatinina en orina de 24 horas menor a la esperada para la edad. La correlación encontrada entre la depuración de creatinina en orina de 24 horas y la fórmula de Cockcroft-Gault fue de 0.88 con p < 0.05. No hubo diferencias estadísticamente significativas al aplicar t de student. La sensibilidad fue de 90.6 por ciento y la especificidad de 79 por ciento. Se concluye que la fórmula propuesta de Cockcroft-Gault puede utilizarse como predictor del grado de filtración glomerular en el paciente geriátrico hemodinámicamente estable