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UTI: Analysis and Microscopic Examination

(excerpt from The Link, volume 4, issue 4, April 2012, published by CMH hospital. This journal is free to physicians in the CMH community)

|Urine analysis |Urine microscopic examinations |

|>1+ protein |Bacteria possible |

|>1+ blood |Bacteria possible |

|Leukocyte esterase |WBC-neutrophils |

|Nitrite |Bacteria-gram negative |

Protein: trace protein is a common observation particularly following exercise and is not significant. However, >1+ protein can be observed with infections

Blood: There is normal excretion of RBC into the urine and trace amounts are not significant. Microbial peroxidase may cause a positive independent of the presence of RBC.

Leukocyte Esterace: This is an indication of neutrophils in the bladder. The neutrophils do not need to be intact and it is possible that they will not be seen in the microscopic exam. Corresponds with pyuria.

Nitrite: this finding in the UA is dependent on the reductase of gram negative bacteria converting nitrate in the diet to nitrite. Yeast and gram positive bacteria will not do this and will not be detected. Also, if there has been insufficient time in the bladder for the conversion the result can be falsely negative (the urine needs to “incubate” in the bladder for about 4 hours for this test to be accurate). Very frequent urination can result in a false negative. Lack of nitrates in the diet can also result in a false negative. Normally, there should be no detectable nitrite.

UA: a positive test (for leukocyte esterace, nitrite or blood) is a reliable index of significant bacteriuria, though a negative test does not exclude bacteriuria (up to date)

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