Question
Prof G, I have been using urine dipstick monitoring as you have recommended, but how do I interpret the results?
Interpretation of dipstick results
The primary reason for starting MS-Selfie was to provide you with the information to self-manage your MS. I have written an earlier Newsletter (Infection 29-Jun-2021)on the use of home dipstick monitoring for the early detection of urinary tract infections (UTIs), so they can be treated early to prevent symptomatic infection or complications such as pyelonephritis (kidney infection) and septicaemia. Please be aware that septicaemia from UTIs is one of the common causes of death in people with advanced MS. I thought I had explained everything when a patient asked me clinic two weeks ago to help him interpret his urine dipstick results.
The following explains what the different tests on a typical urine dipstick mean.
Leukocytes
Leukocytes are the medical term for white blood cells. The test is for Leukocyte esterase, an enzyme produced by neutrophils, the commonest white blood cell. When this is positive, it indicates the presence of white cells in the urine. Please note this test should be interpreted at about 2 minutes after dipping the stick in your urine. A negative leukocyte esterase test is normal. A positive leukocyte esterase test usually means a urinary tract infection. However, any condition that results in haematuria or blood in the urine can result in a positive leukocyte test. This is why it is essential to interpret the leukocyte result with the other tests below, particularly the nitrite, blood and protein tests below.
Nitrites
Nitrites are the breakdown products of some bacteria, and hence positive results indicate a bacterial infection or UTI. However, not all bacteria make the enzyme nitrate reductase so that you can have a nitrite negative UTI. Approximately 20% of culture-positive UTIs are nitrite negative. It takes at least 60 seconds for this test to read out, so please be patient. The absence of nitrites in the urine is normal.
Protein
The protein reagent square indicates the level of protein present in the urine or proteinuria. It also takes about 60 seconds for this test to develop. The absence of protein in the urine is normal. UTIs may cause mild proteinuria. Higher protein levels typically indicated kidney disease and this may be relevant to people with MS; for example, if you have been treated with alemtuzumab new-onset proteinuria in the presence of blood may indicate Goodpasture’s syndrome a rare secondary autoimmune disease as a complication of alemtuzumab treatment.
Blood
The blood reagent square indicates the number of red blood cells, haemoglobin and/or myoglobin in the urine. Myoglobin comes from the breakdown of muscle. Again it takes at least 60 seconds for this test to develop. The absence of red blood cells, haemoglobin and/or myoglobin in the urine is normal. The presence of red blood cells, haemoglobin and myoglobin in the urine may indicate a UTI, but can also be found with kidney or bladder stones and other injuries to the urinary tract, for example, from a poor self-catheterisation technique. Myoglobinuria occurs from rhabdomyolysis or muscle breakdown, which occurs after strenuous exercise in diseased muscle or muscle trauma. Many kidney diseases result in blood in the urine, referred to as nephritic syndrome. Asymptomatic blood in the urine could also indicate a urinary tract or kidney malignancy.
Suppose the test strip starts with a mottled or speckled pattern or remains like this is more indicative of whole red blood cells and suggests lower urinary tract bleeding. Suppose the test strip changes colour more homogeneously. In that case, it indicates free haemoglobin or myoglobin, which suggests the red blood cells have lysed or burst and is more in keeping with upper urinary tract or kidney disease, haemoglobinuria or myoglobinuria.
Glucose
Glucose is a water-soluble sugar molecule, and its presence in the urine is known as glycosuria. This test develops quickly and can be interpreted after 30 seconds. The absence of glucose in the urine is normal. Causes of glycosuria include diabetes mellitus, renal disease and some diabetic medications, particularly the class of drugs called SGLT2 inhibitors. PwMS should not have glucose in their urine, so if you detect glucose please let your HCP know so further tests can be done.
Ketones
Ketones are a breakdown product of fatty acid metabolism. The reagent square should be interpreted after about 40 seconds. The absence of ketones in the urine is normal. However, if you are fasting or on a ketogenic diet, you may find ketones in your urine. The presence of ketones in the urine suggests increased fatty acid metabolism in the absence of fasting and/or a ketogenic diet it could indicate diabetes, i.e. diabetic ketoacidosis.
pH
The pH reagent square represents the acidity of the urine. The normal range: 4.5 – 8.0. The time it takes for this test to develop is 60 seconds. Causes of low urinary pH include starvation, fasting, diabetic ketoacidosis and other conditions that cause metabolic acidosis (e.g. sepsis). Causes of raised urinary pH or alkalosis include some UTIs, conditions that cause metabolic alkalosis (e.g. vomiting) and medications (e.g. diuretics).
Specific gravity
The specific gravity reagent square indicates the amount of solute dissolved in the urine. The normal range: 1.002 – 1.035 mOsm/kg. This test takes approximately 45 seconds to develop. Causes of low specific gravity include conditions that result in the production of dilute urine, such as diabetes insipidus, a condition in which the kidney can’t concentrate urine, kidney disease and excess water intake. Causes of raised specific gravity include dehydration, glycosuria (e.g. diabetes mellitus) and proteinuria from kidney disease.
Bilirubin
Conjugated bilirubin is a water-soluble yellow pigment produced and excreted by the liver in bile. This test also develops rapidly in about 30 seconds. The absence of bilirubin in the urine is normal. The presence of bilirubin in the urine suggests increased serum levels of conjugated bilirubin, which can occur in conditions such as biliary obstruction. The latter can be due to gallstones and more serious conditions such as pancreatic cancer.
Urobilinogen
Urobilinogen is a byproduct of bilirubin breakdown in the intestine and is normally excreted in the urine. The normal range: 0.2 – 1.0 mg/dL. This test takes about 60 seconds to develop. Increased levels of urobilinogen in the urine can be caused by haemolysis or lysis of red blood cells. This occurs in a condition called haemolytic anaemia. Low urobilinogen levels occur with biliary obstruction and would be associated with a positive bilirubin test.
Please note that you need to wait for up to two minutes to read the results of the dipstick, and for UTI monitoring, the leukocyte and nitrite tests are the most important, with backup from the protein, blood and pH tests. If in doubt, take a picture of the test strip with your mobile phone and email it to your HCP for interpretation. I would not recommend daily dipstick monitoring but suggest doing it once or twice weekly. If positive, it is essential to drop off a clean urine sample for laboratory analysis, which we call an MC&S (microscopy, culture and sensitivity). This is to confirm the UTI, culture the bacteria causing the UTI, and test its sensitivity to antibiotics. The specimen you send for MC&S must be done before you start antibiotics; otherwise, the MC&S can give a false-negative result.
I hope this makes sense.
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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust. The advice is general and should not be interpreted as personal clinical advice. If you have problems, please tell your healthcare professional, who will be able to help you.
How to interpret a urine dipstick result