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Oxford University Hospitals NHS Foundation Trust
Microbiology

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Urine samples

Urinary tract infection (UTI) is the result of multiplication of causative bacteria, in one or more structures of the urinary tract, with associated tissue invasion. It can lead to clinical syndromes that include acute and chronic pyelonephritis, cystitis, urethritis, epididymitis and prostatitis. The infection can spread to surrounding tissues (eg perinephric abscess) or to the bloodstream.

Specimen requirements

Samples should be transported to the laboratory as soon as possible. If specimen transport will be delayed, e.g. from primary care, specimens should be stored in a refrigerator until transported to the laboratory.

  • Bag urine
  • Pad urine
  • Catheter urine
  • Clean catch urine
  • Suprapubic aspirate
  • Cystoscopy urine
  • Ureteric urine
  • Ileal conduit urine
  • Urostomy urine
  • Mid-stream urine
  • Nephrostomy urine

Send in a sterile universal container. Label with specimen type.

Urinary catheter tips and unlabelled samples are not processed.

Urine samples for Schistosomiasis

Terminal urine for investigation of Schistosomiasis must be sent no sooner than four weeks after exposure.

Samples should be collected between 10.00am and 2.00pm as this is the period of maximum activity. It is preferable to have the total urine output between these times, as this is when the most eggs are excreted. Alternatively a 24 hour collection of terminal samples of urine can be obtained.

Samples cannot be processed if received in boric acid. If urine cannot be examined within an hour of collection, 1ml of undiluted formalin should be added to the sample to preserve any eggs present within the sample. A minimum of 10ml is the ideal adequate quantity of specimen.

If processing is delayed, the sample should be refrigerated like other urine samples.

Focused testing

Urine should be tested using a rapid reagent diptest for leucocyte esterase activity and nitrite before sending to the laboratory. These tests have equivalent sensitivity and specificity for the diagnosis of UTI as microscopy. If these tests are negative then culture is of limited value.
Microscopy is only performed when any of the following are identified on the request.

  • ? Glomerulonephritis
  • SLE
  • Endocarditis
  • Haematuria
  • Casts (or a diagnosis indicating cast production)
  • Crystals
  • Candiduria
  • Schistosomiasis

Aside from these instances microscopy is of little value.

Please note: urine diptests are not reliable in children under three years old. For this reason all under three year olds are given a urine microscopy to look for white cells, red cells and squamous epithelial cells.

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Turnaround time

The turnaround time for these tests is one to three days.

Laboratory method

Urines are cultured onto chromogenic media and culture results categorised on the basis of quantity and purity of growth. A semi-quantitative culture routine is used which allows an approximation of density of organisms in the bladder urine. Below a recognised threshold (105 cfu/mL) the likelihood is that the organisms grown are contaminants, particularly if more than one organism type is present. Above the threshold it is more probable that a true urine infection is occurring. The most common pathogen isolated from these samples is E. coli.

The A. Menerini Diagnostics SediMAX automated urine analyser is used to identify and quantify the presence of white blood cells, red blood cells and squamous epithelial cells in urine specimens. Requests for casts or Schistosomes are given a manual microscopy.

Where to find results of these tests

  • All results are returned electronically where possible (EPR, SunquestICE).
  • Some results may be phoned to clinicians and GPs.
  • Results are never given directly to patients by the laboratory staff.

Further information and contact details

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