| Which of the following tests included on a urine reagent strip would never be reported out as negative? | View Page |
| A patient suspected of a urinary tract infection has a negative nitrite test, but bacteria is present upon microscopic examination. What may have caused a false-negative result? (Choose ALL of the correct answers) | View Page |
| A voided urine specimen is delivered from the women's clinic to the laboratory six hours after collection. The following results are reported: Color: yellowProtein: negativeBilirubin: negative Clarity: cloudyGlucose: negativeUrobilinogen: 0.2 mg/dL Sp. Gravity: 1.020Ketone: negativeNitrite: positive pH: 9.0Blood: negativeLeukocyte esterase: negativeWhat might these results indicate? | View Page |
| Which of the following substances cause a false positive result for blood on the urine reagent strip? (Choose ALL of the correct answers) | View Page |
| Which of the following substances may cause a false negative result for blood on the urine reagent strip? (Choose ALL of the correct answers) | View Page |
| Nitrite Test The nitrites portion of the reagent strip provides a rapid screening test for the presence of gram-negative bacteria that are often responsible for urinary tract infections. Although urine cultures are still needed to confirm the diagnosis and monitor any urinary tract or kidney infection, the need for a culture may not be obvious because in some cases of early bladder infection, the symptoms may be vague or the patient may be asymptomatic. Diagnosis and treatment of cystitis (bladder infection) is important because if left untreated it may result in kidney damage, impairment of renal function, hypertension and/or septicemia. | View Page |
| Bladder Infections Bladder infections are usually caused by gram-negative bacteria. These bacteria reduce nitrates derived from food to nitrites when urine remains in the bladder three to four hours, sufficient time for this reaction to occur. Nitrite is not present in urine under normal circumstances. When present, nitrites react with p-arsanilic acid to produce a diazonium compound. The diazonium compound in turn couples with 3-hydroxy-1,2,3,4 tetrahydrobenzo-(h)-quinolin to produce a pink color. A first morning, clean, voided midstream specimen is optimal for detecting nitrites in urine. | View Page |
| Test Sensitivity This test is sensitive to 0.06-0.1 mg/dL nitrite ion in urines with a low specific gravity and ascorbic acid concentrations of less than 25 mg/dL. Pink spots or pink edges should not be interpreted as a positive result because some medications can color urine red or turn red in an acid environment. Any degree of uniform pink color should be considered positive, suggesting the presence of 105 organisms/mL. Detection of low levels of nitrite ion may be enhanced by comparing the activated test strip to a white background. It is important to note that color development is NOT proportional to the number of bacteria present. The test is specific for nitrites and does not react with any other substances normally present in urine. Negative results do not necessarily rule out a urinary tract infection because yeasts or gram-positive bacteria unable to reduce nitrites may be the causative agent. | View Page |
| False Positive Results A false positive nitrite test result may occur when a urine specimen has remained at room temperature for an extended period of time, allowing bacterial contaminants to multiply and produce measurable levels of nitrites. Interference from some medications that cause the urine to become red or orange may lead to an incorrect reading of positive for nitrite. | View Page |
| False Negative Results False negative results may occur in urine specimens that did not remain in the bladder a sufficient length of time for the bacteria to reduce a measurable quantity of nitrate to nitrite. Other reasons for false negative results include high specific gravity, ascorbic acid levels above 25mg/dL or low pH (<6). Less frequently, the cause may be due to a lack of sufficient nitrate in the diet (green vegetables) or further reduction of nitrite to nitrogen when large numbers of bacteria are present. In patients receiving antibiotics, the metabolism of the bacteria may be inhibited which would also produce a false negative reaction. | View Page |
| Clinical Significance Early detection of bacteria is important in order to prevent cystitis from developing into inflammation or infection involving the kidney and renal pelvis. The nitrite portion of the test strip can be used to screen individuals who are at risk for developing urinary tract infections, such as diabetics, persons with recurrent infections, or pregnant women. The test is also useful in evaluating the success of antibiotic therapy that is used to treat a bladder infection. | View Page |
| The nitrite portion of the test strip can be used to: (Choose ALL of the correct answers) | View Page |
| Clinical Significance Using the esterase test in conjunction with pH, protein and nitrite provides a combination of tests which can screen for the presence of bacterial infection. | View Page |
| To screen for urinary tract infections leukocyte esterase should be coupled with: (Choose ALL of the correct answers) | View Page |