Frequently Asked Questions

In most cases, it’s recommended to fast for about 8 to 12 hours before a blood test. This means no food during that period (usually overnight until your morning appointment), which helps ensure more accurate results, especially for tests like blood glucose and lipid profile.

Avoid extending your fast beyond 14 hours, as it can cause discomfort. Some tests require a different fasting period—or no fasting at all—so always follow the instructions provided by your doctor or the laboratory. When in doubt, confirm in advance how many hours you should fast for your specific tests.

Yes. You may drink small amounts of water during your fasting period. Staying hydrated with a few sips of water helps circulation and makes blood collection easier, without affecting results. However, avoid drinking excessive amounts (like litres right before the test), as this may slightly dilute your blood. Do not drink coffee, tea, juice, soft drinks, or alcohol, as these can alter test results. In short—moderate water intake is fine during fasting.

Usually, you do not need to stop your regular prescribed medication before a blood test. Medicines for conditions like high blood pressure, heart problems, or thyroid disorders should be taken as normal unless your doctor advises otherwise. Always let the laboratory know what medication you are taking, as some can affect test results. If the medication is not essential (e.g., vitamins or supplements), you can wait until after your blood draw to take it.

Never stop important medication without medical advice. If unsure, consult your doctor ahead of time.

Babies and young children usually do not need a long fasting period. You should always follow the specific instructions from your pediatrician or the laboratory, as some pediatric tests may require special preparation.

A 24-hour urine test involves collecting all the urine you pass over a full 24-hour period. To do it correctly:

• Start in the morning: On the first day, when you wake up, empty your bladder into the toilet and discard this first urine. Note the exact time (e.g., 7:00 am).

• Collect throughout the day: From that moment, collect every drop of urine you pass during the day and night in the container provided. You can urinate directly into the container or use a clean intermediate container to transfer the urine. Do not miss any samples—if you go out, take the container with you or wait until you return home. Keep the container closed in a cool place, ideally refrigerated.

• Finish the next morning: On the following day, at the same time you started (e.g., 7:00 am), pass urine one last time into the container—this completes the 24-hour collection.

• Deliver to the lab: Keep the container sealed and take it to the laboratory as soon as possible. If you miss any urine during the collection period, it’s best to start over on another day, as incomplete samples can invalidate the results.

Following these steps ensures your 24-hour urine sample is accurate, helping your healthcare provider get reliable results.

In the context of laboratory tests, “Urine I” refers only to the physical and chemical examination of the urine (color, appearance, pH, glucose, protein, etc.).

“Urine II” includes both the physical and chemical examination of the urine and the microscopic analysis of the urinary sediment (epithelial cells, leukocytes, crystals, bacteria, etc.).

If in doubt, always confirm with your doctor or with Joaquim Chaves Saúde which specific test is intended, since terminology may vary. The important thing is to ensure that the correct test is performed.

After a risk exposure, HIV may take days to weeks before it becomes detectable – this is called the window period. With modern 4th-generation lab tests (which detect both HIV antibodies and the p24 antigen), infections can usually be picked up within 2 to 4 weeks. On average, by 30 days after exposure, most infections will be detectable. 3rd-generation tests (antibody-only, including many rapid tests) tend to take longer, often detecting infections from 3 to 8 weeks, with confirmation recommended at 3 months if the first result is negative.

If at risk, you can test after about a month, but a negative result should always be confirmed up to 3 months after exposure. Remember: during the window period, a person can still transmit HIV despite a negative result, so precautions are essential.

These terms refer to different types of HIV tests. Third-generation tests (such as many rapid tests) detect only HIV antibodies in the blood. Fourth-generation tests, on the other hand, detect both the antibodies and the p24 antigen, an early marker of the virus.

The key difference is that fourth-generation tests can identify the infection earlier. Antibodies usually take 3 to 6 weeks to appear after infection, while the p24 antigen can be detected as early as 2 weeks after exposure. This means that a fourth-generation test may return a positive result 15 to 20 days after infection, significantly reducing the "window period." In contrast, third-generation tests typically only become positive after 30 days or more.

In summary, fourth-generation HIV tests are more advanced, looking for additional viral components and allowing for faster and more reliable diagnosis. At Joaquim Chaves Saúde laboratories, we use fourth-generation tests for HIV screening, ensuring greater sensitivity and earlier detection.

If you have been in close contact with someone with active tuberculosis, it is important to get tested to check whether you may have contracted the infection—even if you do not yet have symptoms.

From a clinical testing perspective, a molecular test (PCR) for Mycobacterium tuberculosis (MTB) in whole blood is generally recommended, for the following reasons:

Active tuberculosis: PCR is better suited for diagnosing active TB, as it directly detects MTB DNA, confirming the presence of the bacteria.

Immunosuppression: In people with weakened immune systems (such as those with HIV, undergoing chemotherapy, or transplant patients), the IGRA test may produce false negatives because it relies on the body’s T-cell response.

Early detection: PCR can identify MTB soon after infection, whereas IGRA may take several weeks to show a detectable response.

Site of infection: When TB infection is located in an anatomical area with a limited systemic immune response, IGRA tends to perform less effectively.

Genetic variants: Some mycobacterial strains express fewer of the antigens used in IGRA testing, which lowers its sensitivity.

By contrast, the IGRA test is more often used to diagnose latent tuberculosis. It is more sensitive than PCR in detecting latent infection, particularly in extrapulmonary cases, but less sensitive for identifying active disease.

Yes. Taking paracetamol does not interfere with malaria test results. Paracetamol is an antipyretic/analgesic that helps reduce fever and pain but does not affect the presence of the malaria parasite in the blood or the antigens detected by the tests. Studies show that paracetamol does not alter malaria parasite detection.

Therefore, if you have taken paracetamol to relieve fever or discomfort, you can – and should – take the malaria test if you have symptoms or suspicion. Whether by microscopic observation of the blood (“thick drop”/“thin drop”) or by a rapid antigen test, it will still be able to identify Plasmodium if it is present. Just inform the healthcare professional about the paracetamol taken and the dose/time. Keep in mind that paracetamol does not treat malaria, it only relieves symptoms, so testing remains essential for proper diagnosis and treatment.

In women: HPV (human papillomavirus) screening is performed by collecting cells from the cervix, preferably from any suspicious lesions. This is a gynecological exam in which the healthcare professional (doctor or nurse) inserts a vaginal speculum to visualize the cervix and then uses a small brush or spatula to collect cells from the area. The sample is then sent to the laboratory for HPV DNA testing.

For HPV screening in women, the collection is very similar to a conventional Pap smear. You should book the test at a clinic or laboratory that provides gynecology or clinical analysis services, such as Joaquim Chaves Saúde. To ensure accuracy, it’s important not to be menstruating at the time of the test and to avoid sexual intercourse, vaginal douching, or the use of spermicides in the 48 hours beforehand, as these can interfere with the sample.

In men: For screening, HPV testing is usually done on the first urine stream of the morning, before genital hygiene. If suspicious lesions are present, the sample should instead be collected from the lesion itself, either through a swab of the area or a biopsy.

The “window period” is the time between the moment of infection and the moment when that infection becomes detectable by laboratory tests. During this period, a person may already have the infectious agent in their body, but the markers that tests look for (antibodies, antigens, or genetic material) have not yet reached detectable levels. It is essentially the “hidden” time when a test will still give a negative result even though the person is infected.

The length of the window period varies depending on the disease and the type of test. For example, in HIV, the window is typically around 30 days with 4th-generation tests (although in rare cases it may extend to 2–3 months with antibody-only tests). In other infections, the window may last just a few days (e.g., COVID antigen tests) or several weeks (e.g., hepatitis, syphilis ~20–30 days).

During the window period, a person can already transmit the infection to others even if their initial test is negative. That’s why, after a risky exposure, if the first test is negative but still within the possible window period, it is recommended to repeat the test after the window has closed to confirm the result.

A positive result for “Total Hepatitis A antibodies” (Anti-HAV total) means that at some point you had contact with the Hepatitis A virus, but it does not necessarily indicate an active disease. Total antibodies include both IgM and IgG, and the interpretation is as follows:

IgM negative + Total Hepatitis A antibodies positive: indicates past infection or prior vaccination, with immunity developed.

IgM positive: indicates an acute or recent infection (active Hepatitis A).

In other words, you most likely had Hepatitis A a long time ago (often without symptoms during childhood, which is common) or you were vaccinated against Hepatitis A, which left you with IgG antibodies. In that case, you are not sick, just immune.

So, on its own, “Total HAV positive” generally means immunity due to past infection or vaccination. Many adults in Mozambique will show total Anti-HAV positive because they had Hepatitis A during childhood. Therefore, if you do not have a positive IgM or symptoms, you do not have active hepatitis.

If the anti-HCV antibody test (Hepatitis C) is positive, the next essential step is to perform a confirmatory molecular biology test: HCV-RNA (Hepatitis C viral load).

A positive anti-HCV means there has been contact with the virus at some point, but it does not confirm an active infection. It could be an old infection that has already cleared (about 15% of people eliminate the virus spontaneously) or even a false positive result.

The HCV-RNA PCR test detects the virus’s genetic material and quantifies it, confirming whether there is an active infection.

If HCV-RNA is detectable/positive, it means the virus is present in the body, and the patient should be referred for treatment (Hepatitis C is now curable in most cases with antivirals).

If HCV-RNA is undetectable/negative, it indicates there is no active virus.

In either case, a specialist will guide the next steps. But the key test after a positive anti-HCV is the Hepatitis C viral load (PCR) — without it, a diagnosis cannot be confirmed.

The best non-invasive test to detect an active infection by Helicobacter pylori is the urea breath test (H. pylori breath test). In this exam, the patient ingests urea labeled with carbon, and if the bacteria are present in the stomach, they break down the urea, releasing labeled carbon dioxide that can be detected in the exhaled air. It is a simple, safe, and highly reliable test.

Another option is the H. pylori stool antigen test, which is widely used for screening this infection. However, if the result is positive, it is recommended to confirm the active infection with the urea breath test. On the other hand, blood antibody tests are not recommended for diagnosis, as they may remain positive even after the bacteria have been eradicated.

Therefore, to know if you currently have H. pylori, the recommended tests are the urea breath test (preferred) or the stool antigen test. If you are undergoing an upper gastrointestinal endoscopy, it is also possible to test for H. pylori directly from a stomach biopsy (using molecular or histological methods) and assess antibiotic sensitivity — but this is an invasive procedure.

In summary, the urea breath test (13C-urea) is generally the preferred initial exam, as it is simple, sensitive, and precise.

Yes. It is possible to take a DNA sibling test to verify whether two people are biologically related as siblings. This genetic test can determine whether two individuals share a common biological parent (father or mother) – for example, whether they are full siblings, half-siblings, or unrelated by blood.

A sibling test is particularly useful when a DNA sample from the alleged father or mother is not available, and you want to investigate family ties indirectly. The procedure is similar to a paternity test: DNA samples are collected from the individuals involved (usually via saliva/oral swab or blood) and analysed in a laboratory for genetic markers. The more relatives who can participate, the higher the accuracy – sometimes including the mother of both siblings can help clarify results. The laboratory then calculates the probability of sibling relationship based on the genetic matches. Results are usually expressed as a probability (e.g., “the individuals have a 99% probability of sharing the same father/mother”).

At Joaquim Chaves laboratories, we offer confidential, high-precision kinship DNA tests, including sibling testing. If the results are to be used for legal purposes, the test must follow an appropriate chain of custody and may require a court order. For personal knowledge, you can opt for an informational test.

In theory, yes. It is possible to extract DNA from a hair, but there are important conditions: the strand must have a root (hair bulb), and several strands (usually 5 to 10 with roots) should be collected to try to obtain enough DNA. Even then, it is not the preferred method.

Laboratories recommend samples such as blood or saliva (cells from the buccal mucosa) for paternity tests, since they are easier to collect and provide an adequate amount of DNA with a higher success rate. Cut hair (without root) is not useful, as it practically does not contain nuclear DNA. Even hair with roots may sometimes not have sufficient DNA or may be degraded. For this reason, hair is only used when no other type of sample is available (for example, in forensic cases involving a deceased person where only stored hair exists).

At Joaquim Chaves Saúde, paternity tests are performed preferably using oral swabs (saliva) or blood, which are simple, painless, and reliable methods. If only hair is available, forensic analysis can be attempted, but the laboratory must be informed in advance to assess feasibility — and the success rate may be lower, with the possibility of obtaining no conclusive result.

To evaluate diabetes and cholesterol (dyslipidemia), specific blood tests are required.

For diabetes:

Fasting blood glucose: Measures blood sugar levels after at least 8 hours of fasting. Elevated values (≥7.00 mmol/L or ≥126 mg/dL on two occasions) suggest diabetes. It is the basic screening test.

Glycated hemoglobin (HbA1c): Reflects the average blood sugar levels over the past ~3 months. A value ≥6.5% indicates diabetes. It does not require fasting and shows long-term glucose control.

Oral Glucose Tolerance Test (OGTT): May be requested in doubtful cases, assessing the body’s response after ingesting glucose.

For cholesterol:

Complete lipid profile: Includes total cholesterol and fractions (LDL — the “bad” cholesterol, HDL — the “good” cholesterol) and triglycerides. These values help assess cardiovascular disease risk. Although some laboratories now allow the test without fasting, many doctors still prefer 8–12 hours of fasting for greater consistency, especially for triglycerides.

In summary you should do blood tests for fasting glucose and HbA1c to check for diabetes, and total cholesterol, HDL, LDL, and triglycerides to assess cholesterol. Ideally, these tests are done in the morning after fasting, especially for glucose and triglycerides.

All these tests are available at our clinical analysis service. A simple blood sample will reveal whether your levels are normal or altered. With the results, the doctor can confirm or rule out diabetes and check if cholesterol is high, recommending treatment measures if necessary.

Thyroid health is mainly assessed through blood tests that measure thyroid hormones (FT4 and FT3) and thyroid-stimulating hormone (TSH).

These tests make it possible to detect changes in thyroid function, such as hypothyroidism or hyperthyroidism.

To evaluate the pancreas, blood tests for pancreatic enzymes are most commonly used. The two main ones are amylase and lipase. These enzymes help digest food, and their levels rise sharply in the blood when the pancreas is inflamed or injured (e.g., pancreatitis).

Serum amylase: An enzyme that digests starches. In acute pancreatitis, it’s often elevated (>3× the normal limit). It’s usually ordered alongside lipase.

Serum lipase: An enzyme that digests fats. It’s even more specific to the pancreas – high levels indicate acute pancreatitis or other pancreatic problems. Lipase often stays elevated longer than amylase.

If both amylase and lipase are normal, active pancreatitis is unlikely. For the pancreas’s endocrine function (insulin production), glucose and HbA1c tests are used. To assess long-term exocrine pancreatic function (such as pancreatic insufficiency), there are specific stool tests like faecal elastase or fat quantification – but these are only ordered if there are clinical signs (such as fatty diarrhoea).

For your check-up at Joaquim Chaves Saúde, you can request blood amylase and lipase. These are simple tests that can show if there are signs of pancreatic inflammation.

The pancreas has a dual function: exocrine and endocrine.
The exocrine function involves producing digestive enzymes that are sent to the intestine to break down carbohydrates, fats, and proteins. The endocrine function, carried out by the islets of Langerhans, produces hormones such as insulin and glucagon, which regulate blood sugar levels.

To assess pancreatic health, it is important to study both functions. At our laboratory, you can request the “Pancreatic Function” panel, which includes the following tests: Lipase, Pancreatic Amylase, Glucose, OGTT (Oral Glucose Tolerance Test), Insulin, C-Peptide, Trypsin, Chymotrypsin, and Fecal Elastase.

This set of analyses provides a comprehensive evaluation of both the exocrine and endocrine functions of the pancreas.

The rapid pregnancy test (in urine or blood) should be performed on the first day of a missed period or, alternatively, about 10 days after sexual intercourse.

If you choose a urine sample, it is best to use the first urine of the morning and deliver it to the laboratory as quickly as possible.

Quantitative Beta-hCG (human chorionic gonadotropin) testing is a blood test mainly used to confirm and monitor pregnancy. Unlike the qualitative test (which only indicates positive or negative), the quantitative βhCG measures the exact concentration of this hormone in the blood.

It is useful for:

Detecting very early pregnancies, sometimes even before a missed period, since it is more sensitive.

Estimating gestational age approximately, as βhCG levels rise in a predictable way during the first weeks of pregnancy.

Monitoring the progress of early pregnancy, helping to identify if the hormone is increasing as expected.

For example, a doctor may request repeated quantitative βhCG every two days to check whether the values are doubling as they should in a healthy pregnancy, which can help identify possible complications (such as ectopic pregnancy or risk of miscarriage) if the levels do not rise properly.

In addition, quantitative βhCG can be useful after a miscarriage or treatment to confirm that hormone levels have returned to zero. In certain specific cases, it may also be used as a tumor marker, since some rare tumors produce hCG.

In everyday practice, however, its main role is to confirm pregnancy and provide detailed information about its development, with greater precision than a pharmacy test.