Tests on specimens of urine or
In this fourth article in a series on clinical testing, Pamela Mason focuses on common urine and faecal tests that pharmacists may encounter
Identify knowledge gaps
1. List three substances that can be measured
2. Why is mid-stream urine collected?
3. List two tests performed on stools.
Before reading on, think about how this article
may help you to do your job better. The Royal
Pharmaceutical Society’s areas of competence
for pharmacists are listed in ―Plan and record‖,
(available at: www.rpsgb.org/education). This
article relates to ―diagnostic tests‖ and
―therapeutic drug monitoring‖ (see appendix 4 of
―Plan and record‖).
xamation of urine for signs of disease has results of some tests. For example, a container catheter tubing, using a sterile syringe. Urine
E been a diagnostic practice for many
centuries. For example, according to
contaminated with chlorhexidine can result
in false positive results for protein. It is, there-
from catheter bags can be several hours old
and should not be used for testing.
Hippocrates blood or pus in the urine indi- freelance journalist and author, based in fore, best for the patient to be supplied with a
cated ulceration either of the kidneys or of Monmouthshire container specifically for the purpose of
the bladder. Today, urine and stools can specimen collection.
provide information not only about the Pharmacists need to be sensitive to the fact
544 The Pharmaceutical Journal (Vol 272) 1 May 2004
kidneys, bladder and gastrointestinal tract, but that people can have different attitudes towards
also about a wide range of other conditions. handling or talking about body fluids and it is
important for privacy to be maintained.
Urine is produced by the kidneys to remove Midstream specimens Most tests require
soluble waste substances from the body.These that the urine specimen is collected ―mid-
can be detected using dipstick methods (eg, stream‖ (also known as ―clean-catch‖ speci-
tests for pregnancy or diabetic ketoacidosis) mens). This is so that the specimen is not
or, if more detailed information is required, contaminated by bacteria surrounding the ure-
urine can be sent for laboratory analysis. thra — often, these bacteria can be the same as
Some substances can be measured in blood those causing a urinary tract infection (UTI),
or urine (eg, glucose).The main advantage of so can result in a false positive result. First, the
tests on urine is that they are relatively non- skin around the urethra must be cleaned. The
invasive compared with blood tests. However, patient then urinates, pauses, then urinates
if the urine specimen is collected incorrectly, again into the specimen container.
this can affect test results. The correct proce- Not everyone is able to collect their own
dure for collection needs, therefore, to be specimen, particularly if a midstream speci-
explained clearly. It is important that any men is required. Parents may need to help a
container used to collect a urine specimen is child hold the container (urine collection
clean and contains no traces of detergent or bags are used for babies) and people with
disinfectant because these can affect the disabilities or illness may need the help of a
carer. Gloves should be provided to protect
Pamela Mason, PhD, MRPharmS, is a the person collecting the specimen as well as
to prevent cross contamination. In hospital, Visual examination The appearance and
specimens may need to be collected from odour of urine can also suggest health prob-
lems. Normal urine is a clear, straw-coloured
fluid and, often, simply examining a specimen
visually can provide evidence of an infection
or disease. Like other bacterial infections,
UTIs are associated with the recruitment of
the white blood cells to the site of infection.
Pus is formed, which causes urine to become
cloudy. However, cloudy urine is not always a
sign of a UTI and clear urine does not always
rule out infection.
Patients who are jaundiced will have dark
yellow, orange or brown urine because of the
excess bile (often accompanied by pale stools
and yellow skin). Blood can colour urine red
(indicating disease) as can the rare, inherited
disorder porphyria. Some foods, such as beet-
root and asparagus, can also affect the colour
of urine. Drugs that change urine colour
include: levodopa (red), rifampicin (red),
triamterene (blue-green) and vitamin B
complex (dark yellow). Freshly voided urine
has almost no smell, whereas infected urine
has a fishy odour. Urine from people with
anorexia can smell of pear drops.
Pharmacists asked for advice on abnormal
urine colour should check that it is not diet-
Mik e Wyndham Medical P Library
or drug-related. Change
that cannot be clearly Panel 2: Dipstick test results
attributed to foods or
medicines, or that is Bilirubin The presence of bilirubin in urine can
accompanied by unex- suggest biliary disease.
plained symptoms, should
be referred to a GP. Blood Blood is not usually present in urine.
Haematuria (blood in the urine) can be caused by
Dipstick tests Reagent renal conditions (such as glomerulonephritis),
strips, or ―dipsticks‖, are carcinoma and vasculitis (eg, endocarditis,
strips of plastic, with test systemic lupus erythmatosus or other connective
areas treated with chemi- tissue diseases). It can also be caused by
cal reagents. For example, infection (eg, cystitis, prostatitis and urethritis),
a Clinistix strip is impreg- bladder catheterisation, calculi and the use of
nated with glucose cyclophosphamide.
oxidase and an indicator Urine can also be examined for the presence
substance (o-toluidine) of red and white blood cells under a microscope.
which is oxidised to vari- Dipstick and colour chart must be closely compared
ous shades of blue-green, Glucose Glycosuria (sugar in the urine) can be
depending on the amount of glucose present. result in microbial contamination and this caused by diabetes mellitus, pregnancy, sepsis or
Most pharmacists will be familiar with the can affect test results (eg, bacterial consump- renal tubular damage (ie, abnormal renal
dipsticks used by people with diabetes who tion of glucose can give a false negative). absorption).
find blood glucose monitoring difficult (eg, However, samples should be allowed to
Diabur-test 5000), dipsticks used to detect return to room temperature before testing. Ketones Ketones are breakdown products of fats
diabetes and those popular with people on Pharmacists can also advise patients on and their presence in urine can indicate anorexia,
the Atkins diet (eg, Ketostix, see PJ, 27 July keeping records of their test results. dieting or diabetes that is poorly controlled.
2002, pp135–7). Dipstick testing is simple, In addition to contamination, diet and
convenient and offers quick results. Tests can medicines can also sometimes cause false Leucocytes A significant increase in white cell
be performed at home, in surgeries or negatives or false positives. For example, a numbers is evidence of infection, which can be
hospitals and in pharmacies. high ascorbic acid concentration in urine can confirmed by urine culture.
Various dipsticks are available to detect give false negative results with Clinistix.
substances such as glucose, protein and blood. Drugs containing azo dyes (eg, nitrofuran- Nitrites Nitrites in urine indicate infection. The first
Multiple reagent strips are also available. For toin) can also affect the readability of the morning urine, or urine passed at least four hours
example, Multistix 10 SG strips test for biliru- reagent area. after last urinating, is the best specimen to use.
bin, blood, glucose, ketones, leukocytes,
nitrite, pH, protein, specific gravity and uro- Urinary tract infections Assuming that the pH Bacteria will usually increase the pH of urine
bilinogen, to give a comprehensive urinalysis urine has been collected appropriately (ie, it because they break down urea to ammonia,
profile. However, not all of these reagent is not contaminated with the bacteria which combines with hydrogen ions. In terms of
strips are prescribable on NHS prescriptions. normally present in the lower third of the monitoring acid-base imbalance in the body,
Pharmacists can advise patients, who need urethra or anogenital area), bacteria in the serum pH is generally a better measure than
to test their urine regularly to follow the urine indicates a UTI. The dipstick method urine pH.
manufacturer’s instructions on the storage of for detecting UTIs is based on the fact that all Acidic urine is associated with uric acid and
reagent strips as well as use. These should be common bacteria causing UTIs convert calcium oxalate stones. Alkaline urine is
kept in their original container (which often nitrate to nitrite.Thus, an increase in urinary associated with calcium carbonate, calcium
contains a dessicant) and the expiry date nitrite concentration indicates bacterial phosphate, and magnesium phosphate stones.
should be checked. Usually, reagent strips infection. In addition, the enzyme leucocyte Risks can, therefore, be lowered by modifying
should be discarded six months after the esterase indicates the presence of white cells urine pH accordingly.
container is opened. General instructions for and detection of this enzyme provides further Ideally, pH tests should be performed
testing are given in Panel 1. evidence of infection. Dipsticks for UTIs immediately after urine collection. The specimen
If urine cannot be tested within an hour of usually consist of at least two reagent squares, container must be covered to prevent the escape
urinating, it should be refridgerated. one for detecting nitrite and the other for of carbon dioxide.
Prolonged exposure to room temperature can detecting the enzyme.
Although convenient, these dipstick Protein Proteinuria (protein in the urine) can be
methods are limited by the number of false caused by urinary tract infection, diabetes
Panel 1: Dipstick procedure positives they generate so positive results mellitus, glomerulonephritis, nephrosis, pyrexia
should always be submitted for urine culture and pregnancy. A morning specimen is best for
■ Dip the reagent strip into the urine, making (which can take at least two days) to confirm, detecting levels outside the reference range.
sure that the reagent area is completely reliably, the presence of bacteria. A negative
immersed dipstick result, however, is strong evidence Specific gravity Increased urine specific gravity
■ Take the strip out immediately, removing that the patient does not have a UTI. can indicate dehydration, diarrhoea, glucosuria,
excess urine by gently tapping the strip Other conditions that dipstick tests can heart failure (decreased blood flow to the
against the side of the specimen container indicate are shown in Panel 2. kidneys) or renal arterial stenosis. Decreased
■ At a prescribed time after dipping the strip urine specific gravity can suggest excessive fluid
into the specimen (eg, 30 seconds for Diastix pH The body’s control of urine pH is not as intake, diabetes insipidus, glomerulonephritis or
and 10 seconds for Clinistix), closely compare strict as its control of blood pH. Conditions pyelonephritis.
the colour of the test area with the colour associated with high or low pH are listed in
chart provided Panel 2. The efficacy of some medicines is Urobilinogen Small amounts of urobilinogen are
■ After testing, urine can be disposed of in a affected by acidic or alkaline environments so usually present in urine, but raised levels suggest
toilet pH can be used to select the most appropri- liver disease.
ate treatment for a UTI. For example, strep-
www.pjonline.com 1 May 2004 The Pharmaceutical Journal (Vol 272) 545
tomycin and neomycin are more effective in diarrhoea is the result of antibiotic use. This
treating UTIs when urine is alkaline. bacterium grows excessively when antibiotics Action: practice points
alter the balance of colonic bacterial flora and
Specific gravity The specific gravity of urine is can cause pseudomembranous colitis. Reading is only one way to undertake CPD and the
a measure of the amount of substances Recently, a stool antigen test for Helicobacter Society will expect to see various approaches in a
dissolved in the urine (g/ml). It primarily pylori infection has become available. pharmacist’s CPD portfolio.
indicates how well the kidneys are function- 1. Familiarise yourself with the range of
ing to adjust the amount of water in urine. Microscopy and stool cultures Stool dipsticks available and how they should be
specimens can be examined for the presence used.
24-hour urine tests Urine is sometimes of GI infective organisms, such as those 2. Revise the symptoms of bowel cancer and
collected over 24 hours in order to measure a causing food poisoning (eg, Salmonella consider how you would advise a patient with
number of metabolites, such as calcium, species, Staphylococcus aureus and Clostridium a change in bowel habit or stool appearance.
creatinine, nitrogen, oxosteroids, potassium, botulinum), shigella, cholera and giardia. A 3. Make a list of the drugs that can alter the
sodium, urea and urate.The accuracy of such small amount of stool is smeared on to a colour of urine or stools and be sure to
measurements depends, mainly, on the microscope slide and a Gram stain is per- counsel patients about this.
accuracy of the urine collection. formed. The stained smear is then examined
For a 24-hour urine collection required under the microscope for the presence of
from 9am on Tuesday, the patient should be bacteria. The colour, size and shape of cells Evaluate
asked to empty the bladder completely at allow identification of infecting organisms. For your work to be presented as CPD, you need to
9am and discard this specimen. Urine in the Infections can also be identified by placing evaluate your reading and any other activities.
bladder at the start of the test must not be in- a small stool sample in culture media and Answer the following questions: What have you
cluded in the collection.All urine passed after observing bacterial growth. learnt? How has it added value to your practice?
this point is collected. At 9am on Wednesday (Have you applied this learning or had any
the bladder should be emptied completely Faecal occult blood Blood in the stool feedback?) What will you do now and how will this
and this final specimen added to the collec- can come from anywhere along the digestive be achieved?
tion, which is given to the health care profes- tract, from the mouth to the anus. Some con-
sional carrying out the analysis. Analysis must ditions, such as GI ulcers, are associated with
be performed within one hour of collection. heavy bleeding.This can result in stools being colorectal cancer and positive results are
black or ―tarry‖. A black stool usually means bound to cause anxiety. Oral iron prepara-
Stool tests that the blood has come from the upper part tions can also give false positive results. In
A lot of information about a person’s diet and of the GI tract (ie, the oesophagus, stomach or addition to NSAIDs, drugs that can cause GI
general state of health can be gained from duodenum) because exposure to digestive bleeding include anticoagulants, colchicine
stools. For example, a change in dietary habits juices turns the blood black. Stomach or duo- and corticosteroids. Other factors that can
can lead to an increase in the amount of gas denal ulcers caused by non-steroidal anti- cause inaccurate FOB test results include
produced by gastrointestinal (GI) bacteria, as inflammatory drugs are common causes of eating red meat, fish, turnips or horseradish
can acute GI infections (increased gas in the upper GI bleeds. Other causes include gastri- within three days of the test.
intestines due to the rapid movement of food tis and oesophageal varices. Taking iron Screening of asymptomatic people over 45
through the gut) and excessive flatus and stools supplements or bismuth-containing medicines years of age shows that 2 per cent of people
that float are generally associated with these (such as Pepto-Bismol) can also blacken stools. test positive. Of these, one in 10 will have a
conditions. Floating stools can, however, also Bleeding in the lower GI tract can result in carcinoma and one in three an adenoma. A
be associated with malabsorption syndromes. maroon or bright red, bloody stools. Causes series of two or three samples taken over
Increased levels of nutrients in the stool (due include haemorrhoids, anal fissures, diverticu- several days may be a more definite way of
to malabsorption in the GI tract) are supplied lar bleeding, bacterial enterocolitis, inflamma- detecting bleeding in the gut, so sometimes a
to GI bacteria, which produce more gas. tory bowel disease, colon polyps and colon patient might be asked to supply three stool
Bile salts (made by the liver) give stool its cancer. People with such symptoms must be samples for laboratory testing. It should be
a normal brown colour. Cholestasis or liver referred to their GP. remembered that the earlier that diseases, like
infections like viral hepatitis may produce Small amounts of blood in stools may not bowel cancer, are detected the better the
clay coloured stools. Pharmacists asked for be visible but an FOB test should detect this. prognosis. Some health care professionals
advice on a change in stool characteristics FOB tests are mainly used to screen for recommend that all people over 50 years old
should refer patients to a GP if the change has colorectal cancers and polyps. Such tests are should have an annual test for FOB.
persisted for more than two weeks or if also used in people with persistent abdominal
blood, fever, or dizziness accompanies these symptoms (eg, pain). There are two types of Faecal urobilinogen Urobilinogen is
changes. It is likely that the patient will be FOB test. The traditional guaiac smear test produced in the small intestine by the action
asked to collect a stool sample for further involves smearing a sample onto a card, of the intestinal bacteria on bile and it is the
investigation. adding a testing solution and observing a compound which gives the stool its brown
Commonly, stool tests look for blood, colour change (green). Flushable reagent pads colour. Increased faecal urobilinogen levels
urobilinogen and fat or infection. For exam- are also now available. These are convenient are found where there is increased haemoly-
ple, a faecal occult blood (FOB) test can be for home use and there is no stool handling. sis of red blood cells. Decreased levels suggest
requested if a patient has unexplained Many health care providers, however, favour obstructive biliary disease.
anaemia. If a parasitic infestation is suspected guaiac tests because these were used in the
(eg, in prolonged diarrhoea of unknown large studies that have shown the benefits of Faecal fat Tests for faecal fat are used to
cause or other intestinal symptoms) stools are colon cancer screening. help diagnose malabsorption syndromes (eg,
examined for parasites and ova. Although safe and inexpensive, FOB tests pancreatic disease with a deficiency of lipase
Less common stool tests include the are limited by the fact that colorectal cancers and biliary obstruction). If there is steator-
detection of proteolytic enzymes (trypsin and bleed intermittently so tests can give false rhoea (excess fat in the stools), stools will be
chymotrypsin) in young children suspected of negatives. Large amounts of vitamin C can frothy, foul smelling and greasy.This indicates
having cystic fibrosis. Another example is a also cause false-negative results. Moreover, that fats are not being digested.
stool test to detect toxins produced by other lesions can cause blood to be present in It is a misconception that floating stools
Clostridium difficile, particularly in hospital stools (even bleeding gums following a dental are caused by an increase in the fat content of
patients when there is a suspicion that procedure), so the test is non-specific for the stool.
546 The Pharmaceutical Journal (Vol 272) 1 May 2004 www.pjonline.com