The method in use estimates the number of pus and other cells, and the number of bacteria in the urine to help to distinguish infection from contamination.
A midstream urine or catheter specimen is sent to the laboratory in a sterile 30 mL boric acid container.
Urines should be examined within 1 - 2 hours of collection. If this is not possible then refrigeration at 4°C for up to 24 hours is possible for most specimens without much change in bacterial count, but the white cells may become unrecognisable.
Red blood cells may lyse in dilute urine shortly after the specimen being taken: an on site “stick” test will give a more accurate indication of the presence of blood.
Suggestions for the collection of an MSU
Retract the foreskin if necessary, and then pass the first part of the stream into the toilet pan and catch the second part in the container.
If there is a menstrual or vaginal discharge, use of a vaginal tampon is helpful. The patient should be instructed to swab the vulva from the front backwards using a cotton-wool swab soaked in sterile water, whilst separating the labia with two fingers of one hand. Antiseptics must be avoided. Keeping the labia separate, the patient passes the first part of the stream into the w.c. and catches the second part in a sterile container.
Babies and young children
A clean-catch specimen is preferred because urine in adhesive bags is frequently contaminated. Special small volume boric acid containers are available for small paediatric specimens.
Urine for TB culture
3 early morning 150 mL specimens are usually required. These may be delivered to the laboratory as collected or refrigerated each day and taken to the laboratory together. The laboratory supplies suitable containers.
For S. haematobium a complete collection of urine voided between 10:00 and 14:00 is required. At least 3 such specimens should be examined. Serological tests to exclude Schistosomiasis may be requested after 3 months from the last exposure.