Teste de fita de urina

Urine contains waste chemicals from all of the millions of chemical reactions that go on in the body all the time.

However, in some conditions, chemicals that shouldn't normally be present in urine get through the filtering systems in the kidneys and pass into the urine. Normally these chemicals would be dealt with by the kidneys and return to the blood stream.

Urine dipstick tests can be used to see if those chemicals are present.

What is a urine dipstick test?

A urine dipstick test is the quickest way to test urine. It involves dipping a specially treated paper strip into a sample of urine. This can be done during an appointment with a health professional.

The results are usually available within 60-120 seconds. The sample doesn't need to be sent to a laboratory for a urine dipstick test although if the test is abnormal, the sample may be sent to a laboratory for further tests.

A sample of urine will need to be provided in a sterile container. Ideally the urine should be produced straight into the pot. Peeing into another container and then transferring it stops it being a sterile sample so is not recommended.

The best sample is one which is called a amostra de urina do jato médio (MSU). This means starting to pee, then passing the open pot into the stream of urine and then taking it away again when enough urine has been collected. The lid should then be replaced tightly on the pot and then both hands and the pot washed carefully.

A health professional will use a urine testing strip to test the urine. There are several different kinds of urine testing strips that test for different things in the urine. The strip has squares on it that change colour in the presence of certain substances.

The strip will then be compared to a chart on the side of the urine testing strip package. Often the more intense the colour change, the more of the substance there is in the urine.

Some urine dipsticks test for just one or two of the abnormalities below. Others test for many of these substances.

To read the dipstick, this involves:

• Taking a urine sample as above.

• Dipping one of the sticks into the sample, making sure all the test zones on the stick are submerged.

• Removing the stick, tapping to remove excess urine and holding it horizontally so urine doesn't drip.

• After the relevant time (usually between 30 seconds and 2 minutes), holding the dipstick up against the colour chart on the dipstick bottle.

• Each test will be colour-coded and there will be several different shades of that colour. A darker shade indicates that there is more of the relevant substance - blood, glucose etc - in the urine.

• Recording the result.

A urine dipstick test is done for lots of different reasons, such as:

• A routine check during pregnancy to check for glucose, protein or signs of bacteria.

• To screen for diabetes.

• If a infecção urinária is suspected.

• To look for sangue na urina (haematuria).

• It may be done in people with some types of abdominal or back pain to look for kidney or bladder problems.

The first thing that a health professional will do is look at the urine. Normal urine varies in colour from colourless to dark yellow. Various things can affect the way urine looks, from how much fluid has been drunk to what has been eaten recently. The smell can also vary widely and is not a good gauge of illness.

A urine dipstick test can look for the following:

Sangue

• Blood is not normally found in the urine.

• It may be present if there is an infection.

• It can be due to significant underlying disease, such as cancer, in the bladder or kidney.

• In women, it may be due to contamination if menstruating at the time of doing the sample.

• Will usually need to be confirmed by sending the sample for a full laboratory test, as the dipstick test can show a false positive.

Proteína

• Protein is normally found in the urine in tiny amounts but these tiny amounts are usually too small to be picked up on a urine dipstick test.

• Protein may be found in larger amounts if there is an infection.

• It can be seen as one of the signs of pré-eclâmpsia na gravidez.

• It can be the first sign of kidney disease and is also used as a measure of the severity of kidney disease.

Glicose

• Glucose, a type of sugar, is not normally found in the urine.

• It can be found in the urine if someone has poorly controlled diabetes or as the first sign of diabetes.

• It can also be found in people with particular types of kidney disease, even without diabetes.

• There is a rare condition called familial renal glycosuria where glucose is found in the urine without diabetes - this is an inherited condition.

• People with type 2 diabetes who are taking a medicine called an SGLT2 inhibitor (such as canagliflozina, dapagliflozina ou empagliflozina) can have glucose in the urine due to the fact that these medicines help to reduce blood sugar, partly by reducing the amount of glucose reabsorbed into the system via the kidneys. Glucose in the urine whilst taking one of these medicines is normal.

Corpos cetônicos

• Ketones are chemicals made by the body when it's breaking down fat for energy. This happens when starving and the body has used up all, or nearly all, of its stores of sugar (glucose). This is normal.

• Ketones are not usually found in the urine otherwise.

• Ketones may be present in diabetes which is not well controlled; levels of glucose in the blood are usually also very high in this scenario. In someone with diabetes, particularly type 1 diabetes, ketones in the urine can indicate a condition called diabetic ketoacidosis. This is a serious emergency and requires urgent treatment in hospital.

• Ketones may also be present in women who are pregnant.

• Ketones can be a sign of dehydration.

Bilirrubina e urobilinogênio

• Bilirubin and urobilinogen are chemicals produced by the liver. They are not normally found in the urine.

• If bilirubin is found in the urine it usually means there's a problem with the liver.

• Small amounts of urobilinogen may be found in the urine but large amounts suggest a problem with the liver or with glóbulos vermelhos being destroyed too quickly.

Leukocyte esterase and nitrite

• These are both tests for the presence of infection.

• Leukocyte esterase test looks for a reaction that only happens if there are lots of white cells in the urine. White cells get into the urine when there is an infection.

• Nitrite is not normally found in the urine but will appear there if there are lots of bacteria in the urine.

• Nitrite test can be negative even if there are lots of bacteria in the urine if the urine hasn't been in the bladder for long.

• Urine dipstick tests are very accurate at excluding infection but are less reliable for predicting infection - there are more false positive results.

The urine dipstick test also measures how concentrated the urine is and how acidic it is.