Laboratory test for cardiovasular risk assessement (global, hypertension)

Which laboratory tests (from whom) for the assessment of cardiovascular risk?

• Determine the total cholesterol/HDL ratio in all patients older than 50 and in patients younger than 50 (GRADE 1B) with:
  • elevated blood pressure (systolic ≥140 mmHg or diastolic ≥90 mmHg) or who use medication to lower blood pressure;
  • family history of an early ischemic incident;
  • heterozygote familial hypercholesterolemia
• A blood test to assess the cardiovascular risk is not necessary for patients with high risk. These being:
  • documented cardiovascular antecedents;
  • diabetes Type 1;
  • diabetes Type 2 and additional risk factors (micro-albuminuria, hypertension, smoking, and family risk) in patients older than 50.
• Test for micro-albuminuria in patients with diabetes Type 2 (GRADE 1B).

Which laboratory tests after initiation of treatment for elevated cardiovascular risk?

Statins

• Determine total cholesterol and LDL cholesterol before starting statins and after 3 months of treatment in order to check whether the target values have been achieved. If so, annual determination suffices (GRADE 1C).
• Determine GGT and ALT (GPT) before starting and repeat after starting if suspicion of liver toxicity (GRADE 1C).
• Determine creatine kinase (CK) if symptoms that can indicate muscle damage (myopathy and rhabdomyolysis) and with certain risk groups (kidney failure, hypothyreosis, personal or family history of hereditary muscle diseases, antecedents of statin or fibrate muscle toxicity, alcohol addiction, or patients older than 70) (GRADE 2C).

Antihypertensive drug treatment

• Determine potassium and serum creatinine with eGFR (calculated with the MDRD formula) upon the use of diuretics, ACE inhibitors and angiotensin-2 antagonists (GRADE 1C).
• Determine potassium and serum creatinine met eGFR 1) before starting the treatment; 2) 1 to 2 weeks after starting, and 3) after increase of ACE inhibitors and angiotensin-2 antagonists (GRADE-2C)

Which laboratory tests to identify secondary hypertension?

• Determine, depending on the anamnesis and the specific clinical picture, proteinuria, hematuria, and hypokalemia (GRADE 2C).

Which laboratory tests to identify hypertension-related target organ damage?

• Determine fasting glucose, serum creatinine with eGFR (calculated with the MDRD formula) and total cholesterol/HDL ratio (GRADE 1C).
• Check for proteinuria and hematuria.

Which laboratory tests for the follow up of uncomplicated hypertension?

• Determine serum creatinine annually with eGFR (calculated with the MDRD formula).
• Estimate global cardiovascular risk annually (total cholesterol/HDL ratio).
• Determine proteins and microalbuminuria with co-morbidity or alarm signs (GRADE 2C).

Which laboratory tests in the follow-up of hypertension withtarget organ damage?

• For hypertensive patients with non-diabetic kidney diseases (GRADE 2C), determine:
  • serum creatinine with eGFR, potassium, fasting glucose, total cholesterol/HDL ratio (frequency depending on clearing);
  • twice a year: protein creatinine ratio or albumin-creatinine ration in morning urine.
• For hypertensive patients with diabetes mellitus Type 2 (GRADE 2B), determine glycemia, total cholesterol/HDL ratio, and microalbuminuria annually.
• For hypertensive patients with coronary disease, determine glycemia, total cholesterol/HDL ratio annually (GRADE 2C).

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Laboratory test for diabetes mellitus type 2

When and in who to screen for diabetes?

• Screen for diabetes (GRADE 1C):
  • all those 65 and older.
  • 18 to 45 year olds:
• with a history of gestational diabetes
• or with a history of stress hyperglycemia on the occasion of an intervention or hospital admission
• or if two of the following conditions are met:
• given birth to a baby of ≥4.5 kg,
• diabetes in first-degree relatives,
• BMI ≥25 kg/m²,
• waist circumference >88 cm (women) or >102 cm (men).
• chronic corticoid or anti-hypertensive treatment
  • 45 to 64 year olds, if only one of the conditions above is met.
• The screening repetition frequency depends on the glucose levels (GRADE 2C):
  • every three years with normal glycemia (<100 mg/dl);
  • annually with impaired fasting glycemia (100-126 mg/dl);
  • annually with a history of gestational diabetes.
  • With stress hyperglycemia (>126 mg/dl fasting with medical stress such as infection, trauma, surgery, pharmaceuticals), check again outside of the acute period, then annually.
  • Those over 65 are screened annually independently of the glucose level found.

Which laboratory tests used to screen for diabetes?

• Determine fasting glycemia in a venous blood sample. The determination of HbA1c is an alternative (GRADE 1B).

Which laboratory tests used to diagnose diabetes?

• Determine fasting glycemia in venous blood. The determination of HbA1c is an alternative (GRADE 1B).

Which diagnostic criteria for the diagnosis of diabetes?

• Diagnose of diabetes after two fasting gllucose levels (on different days) with a value ≥126 mg/dl (7.0 mmol/L).

Which laboratory tests to identify nephropathy?

• Annually, determine creatinine with eGFR calculated with the MDRD formula (GRADE 1B).
• Annually, determine microalbuminuria in morning urine expressed as per gram creatinine (GRADE 1B).

Which laboratory tests in the follow-up of the cardiovascular risk with diabetes?

• Determine cholesterol annually (total cholesterol, HDL and LDL cholesterol) and triglycerides (GRADE 1B).

Which laboratory tests before starting diabetes medication?

• Calculate the eGFR before starting metformin (GRADE 2C).
• Calculate the eGFR before starting sulfonylurea (GRADE 2C).

Which laboratory tests (and how often) in the follow-up of diabetes?

• Every three months, determine fasting glycemia and HbA1c (GRADE 2C).
• Annually, determine cholesterol (total, HDl + calculated), triglycerides, microalbuminuria and creatinine with eGFR (GRADE 2C).

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Laboratory tests for obesity

Which laboratory tests to assess cardiovascular risk?

• Determine fasting glycemia, total cholesterol, HDL cholesterol and triglycerides (GRADE 1B) in patients with a BMI >30 or a BMI between 25 and 30 in patients with increased cardiovascular risk or patients from 45 years old on with signs of metabolic syndrome (GRADE 1B).

Which other laboratory determinations in obese patients?

• Request no other laboratory determinations unless there are suggestive complaints or signs (fatigue, lethargy, muscle complaints, etc.), or after bariatric surgery (GRADE 2C).

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Laboratory tests for liver disease

When to screen for liver disease?

• Screen:
  • with specific signs of an acute or chronic liver disease (GRADE 1B):
  • with long-term fatigue and/or general malaise with suspicion of liver disease (GRADE 1C).
• Screen, even without signs of a liver disease in the event of:
  • risk of viral hepatitis by sexual risk behavior (GRADE 2C), intravenous drug use (GRADE 2B), blood transfusion before 1992 (GRADE 2C), puncture accident (GRADE 1C);
  • projected long-term use of statins and potentially hepatotoxic medication such as azoles (GRADE 2C).

Which laboratory tests to screen for liver disease?

• Determine GGT and ALT (GPT) (GRADE 1C).
• Determine alkaline phosphatase in patients with elevated GGT and signs of an acute or chronic liver disease (GRADE 1C) (see above).
• Determine, in addition to GGT and ALT, also viral serology if there is a risk of a viral hepatitis (GRADE 2B):
  • HbsAG with sexual risk behavior (GRADE 2C);
  • anti-HCV and HbsAG with intravenous drug use (GRADE 2B) and with puncture accident (GRADE 1C);
  • anti-HCV with blood transfusion before 1992 (GRADE 2C).
• Determine bilirubin when in doubt about the existence of icterus (GRADE 1C).

Which laboratory tests with an increased ALT?

• With ALT (GPT) of <1.5 times the reference value:
  • without liver-related complaints: determine ALT (GPT) again after 1 to 3 months. If still elevated, determine anti-HCV and HBsAG (GRADE 1C);
  • with liver related complaints or risk of hepatitis B or C: determine anti-HCV HBsAG (GRADE 2C).
• With ALT (GPT) from 1.5 to 5 times the reference value:
  • and risk of hepatitis A: determine IgM-anti-HAV (GRADE 1C);
  • and risk of hepatitis B: determine HBsAg (GRADE 1C). If this is negative, determine anti-HBc (GRADE 2C);
  • and risk of hepatitis C: determine anti-HCV (GRADE 1C). If this is negative, and there is a chance of an acute infection, determine HCV-RNA (GRADE 2C);
  • and taking of hepatotoxic medication (statins, azoles, etc.): Again determine ALT (GPT) 1 month after stopping the hepatotoxic medication (GRADE 1C);
  • and hemochromatosis: Determine % transferrin saturation and ferritin with a fasting blood sample (GRADE 2C).
• With ALT (GPT) >5 times the reference value:
  • determine IgM-anti-HAV, anti-HCV and HBsAg (GRADE 1C).
  • If the serology is normal:
• determine HCV RNA with risk of acute hepatitis C infection (GRADE 1C);
• determine CMV-, EBV serology (GRADE 2C);
  • determine also the INR (rapidly deviating with acute liver problems) (GRADE 1B).

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Laboratory tests for pregnancy and preconception

Which laboratory tests to determine pregnancy?

• Determine urine HCG (GRADE 1C).
• Determine serum HCG only with a dubious or unexpectedly negative urine HCG result (GRADE 2C).

Which laboratory tests in the beginning of each pregnancy?

• Determine Hb, RBC and Hct (GRADE 1C).
  • With Hb < 11 g/100 ml, treat with iron substitution
  • With Hb <9.5 g/100 ml, determine the kind of anemia by means of ferritin determination (>30 µg/l).
  • Only after 4 weeks of iron substitution, conduct an Hb electrophoresis if MCV < 80 or if no response.
  • Repeat the Hb, Hct and ferritin determination if no response to the iron supplementation.
• Determine blood group, rhesus factor and irregular antibodies (=indirect Coombs) (GRADE 1B).
• Determine rubella IgG (GRADE 1B).
• Determine toxoplasmosis IgM and IgG, if there is no proof of immunity (GRADE 1B).
• Determine TPHA or ELISA test for syphilis. If abnormal, determine TPPA (Grade 1B).
• Determine HIV antibodies (GRADE 1A).
• Determine HBsAg (GRADE 1A).
• Trace asymptomatic bacteriuria (GRADE 1A).
• Trace proteinuria at each prenatal blood-pressure check.
• Determine HCV antibodies if there is a risk of hepatitis C.
• Screening for CMV is not recommended (GRADE 1C)

Which laboratory tests in the further course of pregnancy?

• Between Week 11 and 14. Determine PAPP-A and free beta HCG (only after 'informed consent') to screen for aneuploidy, in casu Down syndrome (GRADE 1B).
• Between Week 24 and 28:
  • Determine Hb, RBC and Hct again;
  • Doglucose challenge test with 50 g glucose (pregnancy diabetes);
  • Determine again the irregular antibodies (= indirect Coombs).
• Between Weeks 35 and 37: take rectal and vaginal swab to screen for GBS (GRADE 2C).

Which laboratory tests to identify gestational diabetes?

• Do the glucose challenge test with 50 g glucose (GRADE 1C) between Weeks 24 and 28 (GRADE 1A).
• Screen earlier, between Weeks 16 and 18, in patients who have had gestational diabetes or have a high risk of it (BMI >30 kg/m², baby with a birth weight >4.5 kg, diabetes of first-degree relative, ethnicity with high prevalence of diabetes) (GRADE 2C).
• Do not determine glucose (GRADE 1B).

Which laboratory tests are recommended before conception?

• Determine the antibodies against toxoplasmosis (IgM and IgG) and rubella (IgG), if unknown.
• Determine the ABO blood group and rhesus factor D status, if unknown.

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Laboratory tests for unexplained fatigue

Which laboratory tests for unexplained fatigue?

• Request laboratory tests when the fatigue persists for more than one month (GRADE 1B) or in the event of fatigue in patients who are 65 or older (GRADE 1C).
• Determine sedimentation, Hb, fasting glycemia, TSH (including free T4 with deviating result) (GRADE 1B).
• Also determine ferritin in women of child-bearing age (GRADE 2B).

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Laboratory tests for chronic kidney disease

Whom to screen for renal insufficiency?

Screen for renal insufficiency in patients with:

• diabetes (GRADE 1C);
• hypertension (GRADE 1C);
• ischemic heart disease and/or heart decompensation and/or peripheral vascular disease and/or cerebrovascular disease (GRADE 1C),
• family history of renal insufficiency Stage 5 or familial renal diseases (GRADE 2C).

Which laboratory tests to screen for renal insufficiency?

• Determine creatinine met eGFR (calculated with the MDRD formula) (GRADE 1A).
• Determine the albumin-creatinine ratio in diabetics.
• Determine the protein-creatinine ratio or albumin-creatinine ratio in non-diabetics (GRADE 1B).

How often should renal insufficiency be screened for?

• Determine the eGFR in all risk patients annually (GRADE 2C).
• Determine the albumin-creatinine ratio in diabetics annually (GRADE 2C).
• Determine the protein-creatinine ratio or the albumin-creatinine ratio in patients at risk without diabetes. How often remains unclear (GRADE 2C).

Which laboratory tests to diagnose chronic kidney disease?

• Determine eGFR at least three times in 90 days :
  • Check the eGFR within 2 weeks after an initial eGFR result of <60 ml/min/1.73 m2 in order to exclude acute renal insufficiency.
  • Diagnose chronic kidney disease if the eGFR <60 ml/min/1.73 m² for at least 90 days.
• Determine the protein-creatinine ratio or albumin-creatinine ratio with an eGFR <60 ml/min/1.73 m2 (GRADE 1C).
• Determine the stage of chronic kidney disease with the eGFR .
• Determine Hb (if not yet done) from Stage 3B on (GRADE 1C). In this stage, also determine PTH in patients followed in the Care Path(way).
• Determine PTH, calcium, phosphate and vitamin D from Stage 4 on (GRADE 1C).

Which laboratory tests andhow often in the follow-up of chronic kidney disease?

• Regularly determine the eGFR. The correct frequency depends on the clinical situation and the stage (GRADE 1C).
• Annually determine the albumin-creatinine ratio in diabetics.
• Determine the protein-creatinine ratio or the albumin-creatinine ratio to monitor protein urea in non-diabetics. How often remains unclear.

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Laboratory tests for STDs

Who should be screened for which STDs?

• Screen for chlamydia and gonorrhea with heterosexual men and women without a complaint but who are worried after a sexual contact (GRADE 1B).
• Screen in risk groups (men with homosexual contacts, prostitutes, intravenous drug users, patients from areas where HIV or HBV is endemic), for chlamydia, gonorrhea, syphilis, HIV, and, if not vaccinated against hepatitis B virus (HBV), also for HBV (GRADE 1C).

Which laboratory tests to identify a STD (screening and diagnosis)?

Chlamydia (GRADE 1B):

• With an asymptomatic patient: take first-void urine or vaginal swab for an amplification test (for example PCR test) or ELISA.
• With a symptomatic patient: preferably take a cervical or urethral swab (more sensitive than urine) for an amplification test.

Gonorrhea (GRADE 1B):

• With an asymptomatic patient, take a first-void urine for an amplification test (for example, a PCR test or ELISA). If not available, take a cervical or urethral swab for culturing.
• With a symptomatic patient: take a cervical or urethral swab for an amplification test. If not available: take a cervical or urethral swab for culturing.

Syphilis (GRADE 2C):

• Determine TPHA (or ELISA) and TPPA.

HIV (GRADE 2C):

• Determine anti-HIV1 and anti-HIV2 antibodies.

Hepatitis B virus (HBV) (GRADE 2C):

• Determine HBsAg (if not vaccinated).

Herpes simplex virus (HSV) (GRADE 2C):

• Make the clinical diagnosis on the basis of the occurrence of typical painful vesicles that evolve into erosions. If clinically unclear, take a swab for an amplification test or culturing.

Trichomoniasis (GRADE 2C):

• Conduct microscopic examination directly on a vaginal swab or take a swab for an amplification test or culturing.

Hepatitis B virus (HBV) (GRADE 2C):

• Determine HBsAg of a blood sample.

Herpes simplex virus (HSV) (GRADE 2C):

• If clinically unclear, conduct an amplification test or culture on a swab.

Trichomoniasis (GRADE 2C):

• Do a culture or direct examination on a vaginal swab.

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Laboratory tests for thyroid diseases

When to screen for thyroid diseases?

• Request laboratory determinations only when the anamnesis, clinical examination, or family or personal history suggest a thyroid disease (GRADE 1B) or for the diagnosis of atrial fibrillation (GRADE 1B).

Which laboratory tests to detect thyroid diseases?

• Determine TSH (GRADE 1A).
• Determine free T4in case of an aberrant TSH (GRADE 1A).
  • If free T4 is normal with a lowered TSH, determine free T3 to detect a rare T3 hyperthyroidism (GRADE 1B).
  • Determine sedimentation and leukocytes if there is a suspicion of subacute thyroiditis (pain in the thyroid region, fever, and malaise) (GRADE 1B).
  • Determine TSH-R-As if suspicion of Graves' disease (GRADE 1B).

Which laboratory tests and how often in the follow-up of thyroid diseases?

• Determine TSH and free T4 at the earliest six weeks after each dose modification of the drug treatment of hypo- and hyperthyroidism until a stable dose has been achieved.
• After dose stabilization, determine TSH and free T4 every three months for a year (GRADE 2C).
• After one year of stabilization of the dose, determine TSH annually and this life long (GRADE 2C).
• Determine TSH if, during treatment, new complaints or symptoms occur that could indicate a thyroid disease (GRADE 2C).

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Laboratory test for oral anticoagulation therapy

What is the target INR for oral anticoagulation therapy?

• Aim for an INR of 2.5 with virtually all indications (DVT, pulmonary embolism, VKF both chronic and paroxysmal) (GRADE 1A).
• Consult a heart surgeon or cardiologist for a valve-specific INR with mechanical heart valves.
• See to it that the INR deviates no more than 0.5 INR units from the target (GRADE 2C).

How often should the INR with patients on warfarin be determined?

• Determine the INR on the third day after starting the warfarin treatment. Then every 3 to 4 days until a stable maintenance dose has been achieved (GRADE 2C).
• In the follow up:
  • check the INR at least every 4 weeks once stabilization is achieved (GRADE 2C).
  • follow patients older than 75 very carefully in order to keep INR within the therapeutic range, certainly in the event of comorbidity and polypharmacy (GRADE 1C).

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Laboratory tests for specific medication

Which laboratory tests when starting a treatment with statins and in the follow-up?

• Before starting, determine GGT and ALT (GPT). Repeat afterwards only in case of suspicion of liver toxicity (GRADE 1C).
• Determine CK with complaints or symptoms that could indicate muscle damage (myopathy and rhabdomyolysis) and with specific risk groups (chronic kidney disease, hypothyreosis, personal or family history of hereditary muscular diseases, antecedents of muscular toxicity with statins or fibrates, alcohol addiction, or patients older than 70) (GRADE 2C).

Which laboratory tests when starting and following up treatment with diuretics?

• When thiazide diuretics are used, determine potassium and serum creatinine with eGFR (calculated with the MDRD formula).

Which laboratory tests when starting treatment with ACE inhibitors or angiotensine-2-receptor antagonists and in the follow up?

• Determine potassium and serum creatinine with eGFR :
• before starting;
• 1 to 2 weeks after starting;
• Upon increasing of ACE inhibitors or angiotensine-2-receptor antagonists.

Which laboratory tests when starting and in the follow up of treatment with diabetes medication?

• Calculate the eGFR before starting metformin or sulfonylurea (GRADE 2C).

Pre-analytic phase in requesting laboratory tests

What's the best way to take a blood sample?

• Tighten the tourniquet at most one minute and release it as soon as the blood begins to flow in the tube.
• Make sure there is a secure identification system (for example, the name of the patient on each tube).
• Rotate the tube a few times (3-10).

In which order should the samples be taken?

Take the necessary samples in this order:

• serum tube without coagulation activator (red cap and without indication of the coagulation activator on the label
• citrate (coagulation) (blue cap);
• serum tube with coagulation activator (red cap with indication of coagulation activator on the label);
• heparin (green cap);
• EDTA (purple cap);
• fluoride (grey cap).

Which laboratory determinations require fasting?

• Fasting glycemia: eat nothing and drink only water for 8 hours before drawing.
• Triglycerides: eat nothing, drink only water, 12 hours before drawing.
• LDL cholesterol: eat nothing, drink only water, 12 hours before drawing.
• Total cholesterol and HDL cholesterol alone: the patient need not fast.
• Serum iron: in the morning fasting because of the variations throughout the day.
• For all other laboratory determinations: the patient need not fast but it is best to wait 2 to 3 hours after a fat-rich meal.

Storing the blood before pick up?

• Store the blood no longer than 24 hours in the practice.
• Store the blood at room temperature.
• Certainly take account of the following shorter storage times:
  • potassium no longer than 6 hours.
  • phosphorus no longer than 1 hour.
  • PTH no longer than 6 hours, if sample in serum tube.
  • molecular RNA tests (for example, HCV-RNA) no longer than 2 hours at room temperature or 12 hours at 4°C.

How long after taking a blood sample are additional determinations possible?

Laboratory determinations are possible up to 7 days after the blood is taken.

Exceptions:

• 1 day for red blood cells, white blood cells, white blood cell differentiation, platelets, Hb and Hct;
• 1 day for PTH;
• 3 days for TSH;
• 4 days for phosphorus;
• 1 to 2 hours for urine sediment.

What should be taken account of for a reliable potassium determination?

• Take the blood correctly (puncture smoothly, do not have the patient make a fist while the blood is being drawn; keep the tourniquet tight for one minute at most).
• Store at 20 ± 1°C, also during transport from home visits.
• Have the blood transported to the laboratory within 6 hours with the tube erect in a thermally insulated box.
• If these conditions are not maintained, then the laboratory results are not reliable. Look for alternatives: send the patient to the laboratory for blood sampling or take the blood sample in function of the pick up by the laboratory, or arrange for an extra pick up.

What should be taken into account with the collection, storage, and transport of blood for INR determination?

• Plan to collect the blood in the morning (the patient need not fast).
• Collect blood with a 19- to 22-gauge needle. Keep the tourniquet tight for at most one minute, and loosen it as soon as the blood begins to flow into the tube.
• Fill the tube to 90%.
• Rotate the tube immediately after filling 2 or 3 times carefully (do not shake).
• Determine the INR preferably in the 6 hours after collecting the blood.
• Store and transport the blood at room temperature.