Frequently Asked Questions


FAQ´s - Frequently Asked Questions


In this page you can find several frequents questions and answers, with the purpose to assist you with any doubt you may have in the preparation of the analysis collection.

1. Medicines interfere with the Laboratory results?

2. Aspirin changes the tests results?

3. Why aspirin is not included in the medicines list that interfere in the Prothrombin Time test?

4. Why must we not use the first urine discharge when we are going to do a bacteriologic test of the urine contained in the bladder?

5. Is there any incompatibility between the vitamins and the laboratory tests? 

6. And about smoking before a test, any issue?

7. Can we do blood tests with flu, cold or fever?

8. And about electrocardiogram with fever?

9. Menstruation interferes with the tests?

10. The menstruating woman can do laboratory blood tests?

11. The physical effort interferes with the laboratory tests? 

12. Why does the physical effort interfere with the glycaemia dosage? 

13. And the alcohol can change the tests results? 

14. Food also interferes with the results of cholesterol and triglycerides? 

15. How must be the food in order the triglycerides results are reliable? 

16. What is the usual diet requested for some tests?

17. Water "breaks" the fasting?

18. The blood test must always be fasting?

19. The tests requesting fasting must always be done in the morning?

20. Some doctors exempt fasting for some tests but as per the instructions of the Laboratory this is requested. Which instruction must be followed?

21. Can any test be done in the afternoon?

22. And for the tests of stool collection, is fasting requested?

23. For the stool parasitological tests, must the first sample be without laxative?

24. For a urine test, must this be the "first in the morning"?

25. Urine can only be collected in the laboratory?

26. Do the vaginal creams and ova interfere in the urine test?

27. Collecting blood is painful? 

28. Why when the blood collecting for tests, the area becomes sometimes purplish? 

29. After doing my tests, can I have access to the results by phone or by internet? 

30. Can any other one have access to my results without consent?

31. Is the attendance service preferential for children, seniors and pregnant women?

32. What is an antibiogram?

33. The Laboratory has specialised technicians for children collection?

34. Why is not recommended the taking of laxative on the eve of a glycaemic curve?

35. It is really necessary to follow the diet of the laboratory to do a glycaemic curve?

36. Why must we not take in a large quantity of alcoholic beverage to do the faecal occult blood test?

37. Why is recommended to do hormonal tests according to the menstrual cycle?

38. Is it injurious for health to collect children blood repeatedly?

39. Why is done the total dosage of white blood cells? Is not the specific counting the most important? Which are the white cells and what can the levels of each one reveal?


1. Medicines interfere with the Laboratory results?

A few, yes. For instance the antibiotics and the anti-inflammatory interfere with the blood coagulation tests, usually required in preoperative. So, whatever medicines you are taking, inform the collection technician before the collection. If one of them interferes, you need to talk with your doctor about the possibility of suspending it for some days. If the suspension is not possible, this fact must be considered in the assessment of the result.

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2. Aspirin changes the tests results?

Yes, of course. Aspirin is the popular name for the acetylsalicylic acid. This is present in many analgesic and antipyretic.  So, note: all the medicines with acetylsalicylic acid interfere with the blood coagulation tests. In high doses, they can reduce the total values of the thyroxine or T4, one of the thyroid hormones.

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3. Why aspirin is not included in the medicines list that interfere in the Prothrombin Time test?

Because aspirin does not interfere with the coagulation factors assessed in this test. Aspirin interfere with the coagulation system as platelet antiaggregants.

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4. Why must we not use the first urine discharge when we are going to do a bacteriologic test of the urine contained in the bladder?

The first urine discharge brings cells and secretion that may be present in the urethra, namely if there is an inflammatory process and/or infectious called urethritis. When you are concerned about a possible urinary infection (cystitis), it is important that the material tested is not "contaminated" with the one in the urethra. Hence the need for not using the first urine discharge and collect the midstream specimen of urine, that is a urine that well represents the one in the bladder.

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5. Is there any incompatibility between the vitamins and the laboratory tests?

Yes, since they interfere with some tests. For instance, vitamin C changes the calculation of the creatinine. And vitamin E interferes with the results of the platelet aggregation.

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6. And about smoking before a test,

Nicotine interferes with the tests of platelet aggregation and glycaemic curve. In these cases do not smoke in the test's day.

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7. Can we do blood tests with flu, cold or fever?

Yes, of course. Some tests, are even requested exactly because the person has a fever. The intention is verifying if there is any infection responsible for that. However, in some circumstances, the disease responsible for the fever can interfere in the tests intended to assess metabolic and immunologic elements.  In case of doubt, talk with your doctor or laboratory before doing the test.

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8. And about electrocardiogram with fever?

That's fine. But, if this is not urgent, it's better to do the same when you feel better.

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9. Menstruation interferes with the tests?

Yes, for instance with the urine test. So, ideally do it out of the menstrual cycle. But, if this is urgent, urine can be collected, taking two cares: asepsis in the collection and use of vaginal tampon, in order the menstrual blood does not mix with the urine.

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10. The menstruating woman can do laboratory blood tests?

Yes, anyone of them. However, some hormones and some serum proteins may change during the menstrual cycle. So, it is essential that the doctor knows in what period of the cycle the test was done.

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11. The physical effort interferes with the laboratory tests?

A few, yes. For instance, in the dosages of glycaemia and coagulation factor VIII. So, before doing them, you cannot do any physical effort. Besides that, remember: the laboratory tests are standardized for some ideal conditions, well defined. These are the called basal conditions. So, the tests done after physical efforts will eventually have different values from the ones you have in basal conditions.

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12. Why does the physical effort interfere with the glycaemia dosage?

Glycaemia reflects the quantity of sugar in the blood which in turn is an energy source with a quick absorption by the body. So, whenever the body needs more energy, for instance in physical effort and stress, there are important changes in the production speeds and use of sugar. Most often when you do glycaemia dosage tests, we want to know how is the basal level, since the reference value is related with is condition. So, you must be as near as possible of this condition.

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13. And the alcohol can change the tests results?

Yes, namely the triglyceride tests. A dose of whisky, a beer or a glass of wine on the eve is enough to contribute to high your levels, influencing the results. So, ideally, before the test, be three days without drinking any alcoholic beverage. Important: the alcohol also changes the cholesterol, but a little.

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14. Food also interferes with the results of cholesterol and triglycerides?

Yes, namely in the triglycerides. For instance, someone with high triglycerides and that adopts a strict diet on the eve of the test, will have a false too low result. But, someone with normal triglycerides, eating a "feijoada" (stew of beans with beef and pork) on the eve of the test will present a false high result.

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15. How must be the food in order the triglycerides results are reliable?

You must maintain you usual diet during the 5 days before the tests. Fasting during 12 to 16 hours, is essential for the blood collection.

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16. What is the usual diet requested for some tests?

It is the one you usually eat in your daily life. So, this instruction only means the following: do not change your diet.

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17. Water "breaks" the fasting?

No. But it is advised to drink it in moderation. Too much will interfere in the urine tests.

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18. The blood test must always be fasting?

Not all. The simple hemogram, for instance, exempts fasting. But glycaemia and triglycerides need several fasting hours. The fasting time depends on the test.

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19. The tests requesting fasting must always be done in the morning?

Not all. Since you follow the fasting time specified, some of them can be collected in the afternoon, without any problem.

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20. Some doctors exempt fasting for some tests but as per the instructions of the Laboratory this is requested. Which instruction must be followed?

The laboratory practice recommends that, for most of the blood tests, the collection must be done a minimal period of four hours fasting, for the adult individual.  Children and new born children must have a reduced time or even abolished, it depends on the situation. However, for each test, there may be the need for a specific guidance, since the concentration of the substances absorbed, such as glucose varies according to the time after the ingestion of the food. On the other hand, a fasting time too long causes also some changes. Each patient, each test and each case must have their specificities reviewed in order to get the greater level of reliability in the results. If you have any doubt, please follow the Laboratory instructions.

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21. Can any test be done in the afternoon?

Some of them, no. This the case for the cortisol, iron and ACTH (adrenocorticotrophic). These tests must be done necessarily in the morning. Reason: It is in the morning that such substances have the highest level in the body, due to their circadian rhythm.

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22. And for the tests of stool collection, is fasting requested?

No. Also, there is no need for the first defecation of the day. This is valid for all kinds of stool tests. Note: for the customer's comfort it is better to collect the material at home, in a suitable container, provided by the laboratory.

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23. For the stool parasitological tests, must the first sample be collected without laxative?

The 1st sample of the stool parasitological test should be collected without use of laxative in order the stool material can be macroscopically assessed (to look for the presence of mucus, pus and blood, etc.) and also to be done a research technique for larvae of a specific parasite for which there is need the stools are not semi-liquid/liquid.

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24. For a urine test type ll, must this be the "first in the morning"?

Only if requested by the doctor. If this is not the case, the urine can be collected at any time during the day, but please note that before the test: if possible, stay two hours without urinate. It will give the ideal volume for a good collection. This must be ideally collected in suitable container, provided by the laboratory or bought in the pharmacy.

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25. Urine can only be collected in the laboratory?

It depends on the kind of test. For laboratory culture, the ideal situation is the urine collection in the laboratory. But for urine type ll, the most usual, it can be collected at home.

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26. Do the vaginal creams and ova interfere in the urine test?

No, provided there are two cares for not mixing these medicines with the urine:  asepsis in the collection and use of vaginal tampon.

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27. Collecting blood is painful?

Usually, no, since the process takes only a few seconds. But this depends on the sensibility of each patient and of the ability of the technician that collects the blood.

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28. Why when the blood collecting for tests, the area becomes sometimes purplish?

That purplish colour is a haematoma:  overflow of blood from the vein.    This may happen in specific situations, such as: thin and delicate veins, with great pressure; lack of compression in the puncture are; and patient taking some medicine that changes the blood coagulation, among others the aspirin. This is not serious and will disappear within a few days. If needed you can be seen by the clinical pathologist physician that will take the suitable steps.

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29.  After doing my tests, can I have access to the results by phone or by internet?

The results can be informed by telephone only by the clinical pathologist physician, fax, mail or internet, provided the patient consent when the registration.

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30. Can any other one have access to my results without consent?

No. Only someone authorized can have access to the results. Obviously, there are exceptional cases that will be review by the attending physician.

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31. Is the attendance service preferential for children, seniors and pregnant women?

The service for pregnant women, seniors and children is priority. However, in specific situations, it is needed the presence of more specialized technicians (children area, gynaecological area) causing, sometimes, a bit of delay.

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32. What is an antibiogram?

Antibiogram is a test whose purpose is verifying which are the antibiotics more recommended for the treatment of an infection caused by the bacteria isolated in the clinical material assessed. With this test, we know which are the sensitive bacteria antibiotics and to those it is resistant.

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33. The Laboratory has specialised Technicians for children collection?

Yes. The Laboratory has specialised Technicians for children collection. In special cases, the collections will be done by the clinical pathologist physician.

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34. Why is not recommended the taking of laxative on the eve of a glycaemic curve?

A laxative must not be taken since it causes an increase of the velocity of the intestinal transit, changing the absorption. As the absorption of glucose is the basis of the test, this can be negatively impacted.

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35. It is really necessary to follow the diet of the laboratory to do a glycaemic curve?

If it is a poor diet in carbohydrates, present in some food like pasta, sugar and sweets, the answer of the patient can show a more changed profile than with a normal diet.

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36. Why must we not take in a large quantity of alcoholic beverage to do the faecal occult blood test?

The research of faecal occult blood is used to aid the diagnosis of the bowel diseases (mainly of the colon), where there is bleeding. As alcohol is a gastric irritant that can causes bleeding of the stomach due to irritation, the drinking of large quantities of alcohol is not recommended for those that are going to do this kind of test.

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37. Why is recommended to do hormonal tests according to the menstrual cycle?

The recommendation is done for the hormones that are subject to fluctuation as per the cycle day like the LH, FSH, estradiol and progesterone.

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38. Is it injurious for health to collect children blood repeatedly?

The blood collection means to do a puncture of a vein - or in special situations, of an artery - to get a volume of blood to perform the laboratory tests. Sometimes, it is possible to get the needed volume through a digital or heel puncture. In all circumstances, the skin is punctured, what means a small trauma and an injury. There is a small discomfort and a potential risk of contamination. Therefore, the cares involve doing a suitable asepsis in the puncture area and the use if instruments - needles and/or lancets - sterilised. In addition, the practice and the ability of the collection technicians are important. Repeating the process several times is, of course, not appropriate. So, special attention must be given related with the volume of blood collected. The younger the child is, less is the existing volume of blood, and, in proportion, greater is the volume of blood collected.

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39. Why is done the counting of white blood cells? Is not the specific counting the most important?

To have an idea about the number of each type of white blood cells circulating, it is important to have the global and specific counting. Some diseases may cause changes in specific types of white blood cells. So, it is important to know which is the increase or decrease verified in each type of white blood cells.

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