The Chemical Examination segment of Urinalysis analyzes components that require Reagent Strips.
These strips are basically plastic dip-sticks laced with “indicator” chemicals that correspond to a colour change as per a reference range based on the extent of the presence of the specific substance.
Abnormal indicator tests for any of the components mentioned below would require additional testing to reach a conclusive diagnosis.
URINE pH
The pH level indicates how acidic or alkaline your urine is. The pH scale ranges between 0-14 where increasing values correspond to decreasing acidity. A pH value of 7.0 indicates a neutral solution i.e. neither acidic nor alkaline. Normally, urine is mildly acidic. The usual pH value of urine lies between 6.0 to 6.5 but values between 4.5-8.0 qualify as normal. (1)
SUGAR
Usually, urine sugar levels point to urine glucose levels unless pointed-out otherwise. In good health, blood glucose filtered into urine is too low to be detected by lab tests. The normal undetectable range lies between 0 – 0.8 millimoles/L or 0 – 144 milligrams/L).
Presence of even trace amounts of glucose in urine detected at levels over 0.8 millimoles/L [fancy word: Glycosuria] should be taken as an indication to seek medical advice and get screened for Diabetes. Apart from glucose, the presence of other sugars such as fructose or galactose is also abnormal and calls for immediate medical attention.
PROTEIN
Assessment of Urine Protein specifically checks your Urine sample for leakage of proteins that normally circulate in your blood. Such blood proteins, technically called “Plasma Proteins” include Albumin (most commonly assessed), Myoglobin, Globulin, Transferrin etc. Plasma proteins are quite large as compared to the delicate kidney filtration pores where the first stage of segregation of useful and toxic substances takes place, such that these must not pass into the urine at any given instance in good kidney health. Normal urine reports should come up with a “Nil” reading.
Presence of even trace amounts of Plasma Proteins such as Albumin in Urine, commonly called Proteinuria results in turbid, cloudy and frothy urine (the froth does not vanish even after flushing the toilet). This indicates damage to the delicate kidney filtration pores and calls for urgent medical advice. Commonest causes include long-standing Diabetes, High Blood Pressure & Immune system-mediated damage.
Please note:
You may come across the term “Tamm-Horsfall Protein”, or “Uromodulin” in your Urine test reports. This protein forms within nephrons (kidney filtration tubes) beyond the delicate filtration pores. It is usually a normal finding in your Urine Test Reports.
However, do not confuse them with plasma proteins in the blood such as Albumin which cannot cross through the delicate filtration pores into the urine in normal health.
Lab tests may detect significant levels of Tamm-Horsfall Protein in your urinalysis reports if you are dehydrated. Conversely, below-average levels of this protein may be an indicator of Kidney Stones or Damage.
KETONE BODIES
Ketone Bodies or Ketones are “acidic” substances produced by the breakdown of fatty acids in your liver during fasting, starvation, prolonged exercise, while on low carbohydrate diet-plans and as a complication of Diabetes mellitus. In good health, our heart and brain utilize these ketones as fuels such that there is no or extremely low levels of ketone-body-excretion in Urine. Standard lab kits are unable to detect such trace amounts. Normal urinalysis reports produce a “Nil” reading for Ketone Bodies. Their presence in Urine gives it a characteristic “fruity” odour to it & points to excessive levels of Ketones in our blood. This calls for an urgent evaluation for Diabetes mellitus (usually Type1) by your doctor.
BILIRUBIN
Bilirubin is a chemical that enters our blood circulation when red blood cells (RBCs) start to rupture (hemolysis) after completing their designated lifespan. Normally, Bilirubin travels to our Liver to make Bile and aid in fat digestion in our food. This eliminates the need for our Kidneys to remove bilirubin in Urine in good health. Presence of Bilirubin in Urine indicates an excess of it in our blood, gives an abnormal Amber colour to our urine and may point to liver disease or abnormal, excessive red blood cell breakdown. Urgent Medical care is necessary here.
UROBILINOGEN
Bacterial enzymes in our intestine break down Bilirubin (as mentioned above) to form Urobilinogen. Part of it normally passes out in our Urine. Presence of up to 1.0 mg/dL of Urobilinogen in your urinalysis report is normal.
OCCULT BLOOD
In good health, Urine must be free of any blood at any instance. The technical term for the presence of blood in urine is Haematuria. This could range from minute quantities such that it is invisible to the naked eye (occult or hidden bleeding) traced by chemical dip-sticks, to frank haematuria such that the urine assumes reddish tinge to cola-coloured appearance. However, irrespective of the quantity, blood in urine is abnormal and warrants immediate medical intervention.
NITRITE
Healthy Urine Samples contains chemicals called NITRATES in it. In the presence of a Urine Infection, NITRATES chemically convert to abnormal NITRITES. Therefore, normal urinalysis reports should be “negative” for Nitrites. If Nitrites show up in your Urinalysis report, it indicates urinary tract infection or sample contamination.
ASCORBIC ACID
Ascorbic Acid is the chemical name for Vitamin-C. It is a water-soluble vitamin that filters freely into nephrons when it’s level in the blood exceeds normal limits. This can happen in individuals who take Vitamin-C fortified diets or supplements.
Chemically, Vit C is a strong reducing agent. Hence, when present in urine, it can interfere with and give False Negative results for other dipstick tests. This is especially true for Urinary Glucose measurements. Hence, laboratories assess Ascorbic acid levels as a precautionary measure to avoid missing even trace levels of any of the other components which may otherwise help to substantiate a clinical diagnosis early on. (2)
Click on the image links below to learn about the parameters routinely checked during the “Physico-chemical Examination” and “Microscopic Examination” of your Urine Sample.
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