Urine production is the process of eliminating waste products and toxic substances to maintain fluid balance in the body (McLafferty et al, 2014). Urinalysis using a reagent test strip (Figure 1) is an inexpensive, simple and non-invasive procedure to assess the health status of an individual by measuring elements found in the urine such as electrolytes, hormones or waste products of metabolism (Yates, 2016).
Urinalysis is often carried out at routine medical examinations or by a midwife during pregnancy. It can be used in combination with other more invasive testing to detect conditions such as diabetes, acute kidney injury, chronic kidney disease, urinary tract infection, dehydration and pre-eclampsia. It is also regularly used in pre-surgical preparation, or on acute or planned hospital admission. Urine is routinely tested on first contact to form a baseline for future assessment (Royal College of Nursing (RCN), 2016a). Frequency thereafter will depend on the rationale for testing and the person's general health status.
Sample collection
There are various methods of urine collection, including:
For the most reliable results, urinalysis should be performed immediately following voiding. If this is not possible, then it should be carried out within 2 hours (Dougherty and Lister, 2015; Collie et al, 2018).
Preparation and equipment
It is vital that the health professional understands the rationale for undertaking the urinalysis, and has the necessary competence to perform the procedure with comprehensive knowledge of the equipment required (Table 1).
| Equipment | Rationale |
|---|---|
| Gloves and aprons | Avoid direct contact with bodily fluids |
| Urine test strips | Reagent strips to detect elements present |
| Sterile container | To collect sample and avoid cross contamination |
| Sterile gauze | To blot the underside of the test strip |
Reagent test strip procedure
Before the procedure
During the procedure
After the procedure
Interpreting results
The health professional should ensure that they are fully aware of the implications of completing a urinalysis and understand the results. It is important to examine the urine for odour, colour and clarity before undertaking urinalysis with the test strip, as these can provide indications of a patient's health status (Yates, 2016) (Table 2).
| Odour | |
|---|---|
| Normal: Freshly voided urine may have a slight but inoffensive smell Some foods can produce an odour in the urine, for example, asparagus | |
| Observation | Potential indication |
| Fresh fish–ammonia smell | Urinary tract infection |
| Pear drop–acetone smell | Presence of ketones |
| Colour | |
| Normal: Pale straw to a deep amber colour, depending on concentration of urine There are several factors that may alter the colour of urine, including various medications and foods (eg beetroot, food colourings, senna-based laxatives, antibiotics) | |
| Observation | Potential indication |
| Dark urine | Dehydration |
| Strong yellow/brown/green | Presence of bilirubin |
| Green | Pseudomonas infection or excretion of cytotoxic drugs |
| Red-brown, bright red | Blood (haematuria); however, menstruation should be ruled out in females |
| Clarity | |
| Normal: Clear, although urine may also be cloudy and still normal Clarity is usually reported on a scale from clear, to slightly cloudy, cloudy and finally turbid | |
| Observation | Potential Indication |
| Cloudy | Mucus, sperm, prostatic fluid, skin cells, white or red blood cells, pus or bacteria |
| Frothy | Presence of protein |
Source: Yates, 2016; Mayo Clinic, 2017; Lab Tests Online, 2018
Interpreting the results requires an understanding of the clinical implications of the individual reagent squares. Urinalysis using a reagent strip can be subjective given that, on occasion, some squares may present with a colour between the negative and the lowest positive and individual interpretation of this may be distinctively different (Newson, 2016).
Leucocytes
The test strips detect leucocyte esterase, an enzyme produced by white blood cells. In the context of urine testing, these are usually neutrophils, and their presence may be a sign of pyuria associated with a urinary tract infection (UTI), although sometimes it may indicate a more severe renal problem (Bardsley, 2015).
Nitrites
These are not typically present in urine, and they can be associated with the presence of bacteria that can convert nitrate into nitrite, suggesting a potential UTI. However, the absence of nitrites does not always rule out a UTI, as there is the potential for a false negative result (Devillé et al, 2004).
Bilirubin and urobilinogen
Bilirubin is not normally present in urine. It is produced when red blood cells are broken down by the liver, and is a component of bile. Therefore, the presence of bilirubin in urine can indicate liver damage. In the gut, bilirubin is broken down to urobilinogen, some of which goes back into the bloodstream and is excreted in urine. Higher than normal levels of urobilinogen may suggest liver disease and lower than normal levels may indicate gallstones (RCN, 2016a).
Protein
Urine does not routinely contain a level of protein detectable on a urine reagent strip (in a healthy individual). Damage to the glomerular filtration barrier in the kidneys leads to proteinuria, and this may be caused by kidney damage, hypertension, diabetes or pre-eclampsia in pregnancy (Mulryan, 2011).
pH
All urine will give a pH reading on analysis, and it is usually slightly acidic. A range of 4.5–8.0 is considered normal (RCN, 2016a). Extremes of acidity may indicate formation of urinary stones, while alkaline urine may indicate a urinary tract infection with certain types of bacteria, such as Proteus mirabilis, Klebsiella or Pseudomonas (Higgins, 2007). However, diet and medication can also alter pH.
Blood (haemoglobin)
Blood in the urine (haematuria) at a level that can be detected by reagent strips would be an abnormal finding (Yates, 2016; Lab Tests Online, 2018). It may indicate the presence of kidney disease, kidney stones, tumours, infections or trauma to the urinary tract (RCN, 2016a). It is important to remember that it may also be a consequence of cross-contamination, for example, vaginal bleeding during menstruation.
Specific gravity
This identifies how dilute or concentrated the urine is (Lab Tests Online, 2018). Someone who is well-hydrated will have dilute urine, with a lower specific gravity, whereas dehydration will produce a concentrated urine, with a higher specific gravity.
Ketones
Not normally present in the urine, these form during the abnormal breakdown of fat instead of glucose for energy (NHS website, 2016). This can be caused by prolonged vomiting, such as in pregnant women with hyperemesis gravidarum, or fasting and starvation (NHS website, 2016; Yates, 2016). However, ketones can also be detected during dieting, episodes of diarrhoea, or as a sign of raised blood glucose, such as in poorly controlled diabetes, which can result in diabetic ketoacidosis (increased acidity of the blood) (RCN, 2016a; Yates, 2016).
Glucose
This may be detected in pregnancy as a consequence of a reduced renal threshold and increased renal blood flow (Newson, 2016). Glycosuria is not normal and can be indicative of an endocrine abnormality, such as diabetes, gestational diabetes or steroid-induced diabetes (Great Ormond Street Hospital, 2015); however, urinalysis alone will not be diagnostic.
Summary
Urinalysis is a common practice and as such, health professionals must have the necessary skills to competently collect the specimen and carry out the procedure while limiting the risk of contamination by using the test strips accurately. They must possess the skills to interpret findings in combination with the presentation and clinical history of the patient, remembering that further testing may be required to provide a more definitive diagnosis.