Specimen Collection 1. Obtaining a Midstream Specimen of Urine
Specimen collection is the process of obtaining tissue or fluids for laboratory analysis or near-patient testing. It is often a first step in determining diagnosis and treatment (Dougherty and Lister, 2004). The process must minimise health and safety risk to all staff handling the sample and the risk of erroneous data/results. This article, the first in a six-part series on specimen collection, details how to collect a midstream specimen of urine (MSU).
Dan Higgins, RGN, ENB 100, ENB 998, is senior charge nurse in critical care, University Hospital Birmingham.
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Good practice principles
The specimen must be:
- Appropriate to the patient’s clinical presentation;
- Collected at the right time;
- Collected in a way that minimises contamination;
- Collected in a manner that reduces risk to all staff (including laboratory staff);
- Collected using the correct tools;
- Documented clearly, including the process;
- Stored/transported appropriately.
The collection of any tissue/fluid carries a risk to staff from splash or inoculation injury, so practices such as universal infection control procedures, as outlined by the RCN (2005), should be followed.
Urine is frequently collected for microbiological and/or biochemical investigation. It is commonly collected for:
- Testing levels of particular metabolites or presence of particular drugs or drug metabolites, for example hormone metabolites and toxicology screens in the poisoned/overdosed patient;
- Microbial culture and antimicrobial sensitivity;
- Point of care urine analysis (urine dipsticks).
In most cases, particularly where a sample is to be microbiologically tested, an MSU is required. This involves taking a ‘middle’ sample while the urine is being voided, avoiding the initial and end stages of the void.
This method reduces the risk of sample contamination from bacteria colonised around the distal urethra as these bacteria are washed away with the initial urine flow.
Minimising bacteria in the sample may prevent bacterial multiplication in storage, making erroneous results less likely.
Midstream urine specimens are indicated in adults and children who are continent and can empty their bladder on request (Gilbert, 2006). Most patients need education to ensure that a midstream sample is collected and advice on hygiene before the procedure to prevent contamination from hands or the genital area.
While routine skin cleansing of the genital area before the procedure appears to make little difference in contamination rates (Leaver, 2007; Gilbert, 2006), the principles of good hand and genital hygiene should be promoted.
Uncircumcised men should be instructed to retract the foreskin before micturition. Women should be instructed to part the labia (Graham and Galloway, 2001).
There appears to be an agreement that a strong urine flow is more effective in clearing bacteria from the urethral meatus (Leaver, 2007; Gilbert, 2006). This would suggest that obtaining the sample when flow can be optimised (when the bladder is full) will result in the least contaminated sample. Thus the most appropriate time to collect a sample is when the bladder is full.
The following items should be collected:
- Soap and water;
- Sterile specimen pot (preferably with a wide opening);
- Gloves/plastic apron;
- Appropriate forms/documentation.
- Obtain informed consent, explain procedure to optimise quality of collected specimen (Fig 1).
- Assess what level of assistance the patient may require.
If no - or minimal - assistance is required:
- Instruct patient to wash hands and attend to genital hygiene as required (Fig 2);
- Provide information on parting the labia/retracting the foreskin as appropriate;
- Instruct the patient to direct the first part of the urine void into the toilet (Fig 3). Ask the patient to collect the middle part in the sterile pot (Fig 4);
- Ask the patient to void remaining urine into the toilet (Fig 5);
- Instruct the patient to wash hands;
- Complete the documentation, specimen pot, accompanying form and notes (Fig 6);
- Dispatch the sample to the laboratory immediately or, if storage is required, refer to organisational policy.
If assistance is required:
- Wash hands;
- Don protective gloves and apron;
- Instruct the patient to commence voiding;
- During the middle of the void (as indicated by the patient) place the sterile specimen pot to collect the urine flow;
- Allow the patient to finish voiding;
- Wash hands and remove apron;
- Complete the documentation, specimen pot, accompanying form and nursing notes.
This procedure should be undertaken only after approved training, supervised practice and competency assessment, and carried out in accordance with local policies and protocols.
Dougherty, L., Lister, S. (2004) The Royal Marsden Hospital Manual of Clinical Nursing Procedures. Oxford: Blackwell Publishing.
Gilbert, R. (2006) Taking a midstream specimen of urine. Nursing Times; 101: 18, 22-23.
Graham., J.C., Galloway, A. (2001) The laboratory diagnosis of urinary tract infection. Journal of Clinical Pathology; 54: 911-919.
Leaver, R.B. (2007) The evidence for urethral meatal cleansing. Nursing Standard; 21: 41, 39-42.
RCN (2005) Good Practice in Infection Prevention and Control: Guidance for Nursing Staff. London: RCN.
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