Scientific tests

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Chapter 41 Scientific tests

Chapter contents

Blood tests 331
Qualitative analysis in brief 338

Blood Tests (Table 41.1)

The initial batch of blood tests will be a full blood count and erythrocyte sedimentation rate (ESR) which indicates inflammation or disease. Blood tests are not conducted randomly and cost is often an issue, so more expensive tests will be run only when a more definitive diagnosis is required.

Table 41.1 Normal adult ranges in common diagnostic tests.

Test Normal Range
  Males Females
FULL BLOOD COUNT
Red blood cells 4.5–6.5 1012/L 3.8–5.0 1012/L
Haemoglobin 13–18 g/100 mL 11.5–16.5 g/100 mL
Hct 45–52% 37–48%
MCV 80–96 femtoL 80–96 femtoL
MCH 27–32 pg 27–32 pg
MCHC 32–36 g/dL 32–36 g/dL
RDW 11–15% 11–15%
White blood cell count 4–11 109/L 4–11 109/L
Neutrophils 2.0–7.5 109/L 2.0–7.5 109/L
Lymphocytes 1.3–4.0 109/L 1.3–4.0 109/L
Monocytes 0.2–0.8 109/L 0.2–0.8 109/L
Eosinophils 0.04–0.44 109/L 0.04–0.44 109/L
Basophils 0.0–0.109/L 0.0–0.109/L
Platelets 150–440 109/L 150–440 109/L
AUTOMATED WHITE CELL DIFFERENTIAL
Segmented neutrophils 34–75% 34–75%
Band neutrophils 8% 8%
Lymphocytes 12–50% 12–50%
Monocytes 3–15% 3–15%
Eosinophils 5% 5%
Basophils 3% 3%
Prothrombin time 10–15 s 10–15 s
LIVER FUNCTION TESTS
Bilirubin 0–21 micromol/L 0–21 micromol/L
Serum alkaline phosphatase 20–125 iu/L 20–125 iu/L
ALT/SGPT 0–40 iu/L 0–40 iu/L
ALT/SGOT 0–48 /L 0–48 IU/L
GGT 0–45 IU/L 0–45 IU/L
Total serum protein 59–82 g/L 59–82 g/L
Blood Lipids
Total cholesterol >200 mg/dL >200 mg/dL
HDL <37 mg/dL <47 mg/dL
LDL >130 mg/dL >130 mg/dL
Triglycerides >150 mg/dL >150 mg/dL
Ferritin 18–270 ng/mL 18–160 ng/mL
Fasting glucose 60–109 mg/dL 60–109 mg/dL
UREA AND ELECTROLYTES
Serum sodium 133–145 mmol/L 133–145 mmol/L
Serum potassium 3.5–5.3 mmol/L 3.5–5.3 mmol/L
Serum urea 2.5–6.6 mmol/L 2.5–6.6 mmol/L
Serum creatinine 45–110 lmol/L 45–110 lmol/L
Erythrocyte sedimentation rate (ESR) >15 mm/h >20 mm/h
Rheumatoid factor 0–35 IU/mL 0–35 IU/mL
HORMONAL LEVELS
Serum TSH 0.3–3 mIU/L 0.3–3 mIU/L
Serum thyroxine T4 (protein bound) 4.6–12 lg/dL 4.6–12 lg/dL
Free T4 (FT4) 0.7–1.9 ng/dL 0.7–1.9 ng/dL
Serum triiodothyronine (protein bound) 80–180 ng/dL 80–180 ng/dL
Free T3 (FT3) 230–619 pg/d 230–619 pg/d
Serum prolactin N/A 0 to 20 ng/mL
Serum LH N/A 5–20 mIU/mL
Serum FSH N/A 5 –30 mIU/mL
Serum FSH after menopause N/A 50–100 mIU/mL
KEY VITAMIN AND METABOLITES
Serum B12 150–600 pmol/L 150–600 pmol/L
Red cell folate 360–1400 nmol/L 360–1400 nmol/L
Homocysteine 5–15 lmol/L 5–15 lmol/L
METALS    
Copper >20 mg/dL >20 mg/dL
Urinary copper <100 μg/24h <100 μg/24h

Blood test results are now being delivered directly to the doctor’s surgery by computer and abnormalities are identified by the laboratory, although normal ranges are demonstrated by the side of each test.

Full Blood Count

This is performed if there is:

• suspected blood disease
• inflammation
• cancer
• infectious disease.

Babies under 1 year and pregnant women can also be screened this way.

White Blood Cell Count (WBC)

• The number of white blood cells in a volume of blood.

A clinical condition known as leukopenia can occur where the bone marrow produces very few white blood cells. This reduces the efficiency of the immune system, leaving the body open to infection. This can be the result of exposure to:

• Gamma radiation.
• Drugs (such as chloramphenicol on rare occasions).
• Carcinogenic chemicals: e.g. chemicals that contain benzene.

Automated White Cell Differential

This allows the practitioner to see a breakdown in percentage of the different types of white blood cells.

Red Cell Count (RBC)

• The number of red blood cells in a volume of blood.
• An increase in the RBC can occur for several reasons:

• living at high altitudes
• strenuous physical training
• smoking.

• Certain drugs have been associated with an increased RBC, e.g. gentamicin and methyldopa.

Haemoglobin (Hb)

• The amount of haemoglobin in a volume of blood.
• A low value indicates anaemia.
• A low haemoglobin value should always be considered alongside the components of the full blood count.

Haematocrit (Hct)

• The ratio of the volume of red cells to the volume of whole blood.
• If raised, can indicate reduced plasma volume, possibly due to dehydration, e.g. drug (diuretic) or alcohol induced. Might also indicate increased red cell mass due to certain types of tumours.

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• Mean Cell (Corpuscular) Volume (MCV)

• The average volume of a red cell (how big is it?).
• Low in microcytic anaemia, found in iron-deficient anaemia (see Chapter 28 ‘Blood disorders’, p. 209).
• High in macrocytic anaemia, found in pernicious anaemia (see Chapter 28 ‘Blood disorders’, p. 210).

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• Mean Corpuscular Haemoglobin (MCH)

• This is the absolute amount of haemoglobin in the average red blood cell in a tested sample.
• Usually, however, a combination MCV and MCHC is more useful:

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• Mean Corpuscular Cell Haemoglobin Concentration (MCHC)

• Calculated from the haemoglobin measurement and the haematocrit.
• The average amount of haemoglobin in the average red cell.
• Calculated from the measurement of haemoglobin and the red cell count.
• Low in microcytic (hypochromic) anaemias.
• Normal in macrocytic (normochromic) anaemias: this is because although the cell size is larger than normal the amount of haemoglobin is high therefore making the concentration normal:

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• Red Cell Distribution Width (RDW)

• Measures the variability of red cell size, therefore a high number indicates greater variation in size.
• A high RDW with a normal MCV can indicate iron, vitamin B12 or folate deficiency.
• Normal range is 11–15%.

• Platelet Count

• The number of platelets in a specific volume of blood.
• Platelets are not complete cells: they do not contain a nucleus and are actually fragments of cytoplasm from a cell found in the bone marrow called a megakaryocyte.
• Platelets play a vital role in blood clotting.
• Patients with liver disease develop an enlarged spleen: platelets then become trapped in the small pathways of the spleen, as the spleen is so large. The platelet count then reduces.
• Thrombocytopenia might also be due to failed platelet production (leukaemia, aplastic anaemia), increased platelet destruction or use or dilution of platelets.

• Ferritin

Ferritin is a protein in the body which binds to iron. Most of the iron in the body is bound to ferritin, which is found in the bone marrow, liver, spleen and skeletal muscle. There is not much ferritin in the blood.

Under normal circumstances, serum ferritin most closely indicates the amount of iron stored in the body. Serum ferritin is the most convenient way to estimate iron stores in the body.

If ferritin levels are too low, anaemia due to iron deficiency arises from the following causes:

• Excessive menstrual bleeding.
• Pregnancy.
• Low iron in the diet (vegetarians and vegans).
• Bleeding from the gastrointestinal tract: ulcers, colon cancer, haemorrhoids.

If ferritin levels are too high:

• The amount of iron in the body is too high: this indicates an iron overload disorder such as haemochromatosis or porphyria (see Chapter 28 ‘Blood disorders’, p. 211).
• Iron might be in excess because the body is sequestering iron in the form of ferritin to deprive bacteria of it: a C-reactive protein (CRP) test is used to see whether the elevated ferritin is due to infection or other causes. Both the CRP and the ferritin are made in the liver in response to inflammation. They are known as acute-phase reactants.

• C-Reactive Protein

This is a plasma protein, levels of which increase due to inflammation. If found to be present, it is an indicator for:

• cardiovascular disease
• hypertension
• diabetes
• rheumatoid arthritis
• infectious diseases
• autoimmune conditions: e.g. systemic lupus erythematosus.

• Glucose

This test usually occurs first thing in the morning, with the patient having fasted since the night before. An abn s above 7 mmol/L. However, it is possible for a patient with a normal glucose metabolism to have a ‘false positive’ due to the following.

Oral Glucose Tolerance Test (OGTT)

This is run when both a urine sample and a blood test indicates a problem with metabolizing glucose. It differentiates between a patient who might have had false positives and a normal pattern of glucose fluctuation and a diabetic pattern due to pancreas malfunction or insulin resistance.

• The patient fasts overnight before a sample of blood is taken.
• The patient then drinks 75 g of glucose dissolved in 250–350 mL of water.
• After 2 hours, another blood sample is taken.
• The levels of glucose in the two samples are compared.

The patient is considered to have a problem with glucose metabolism if the levels of glucose in the fasting blood sample are more than 7 mmol/L; if the OGTT is between 7.8 mmol/L and 11.1 mmol/L the patient is deemed to have impaired glucose tolerance; above 11.1 mmol/L and the patient is said to have diabetes.

In a patient able to process glucose normally, the glucose concentration approximately doubles in the first hour, returning to normal after 2 hours. The blood glucose in a diabetic patient will rise to a high level and takes more than 3 hours to return to normal.

The tests for glucose are normally combined and other aspects of the case history taken into account. False positives can occur particularly in women with gestational diabetes postpartum.

• Electrolytes

The electrolytes potassium, sodium and chloride are important for maintaining the:

• correct amount of fluids in the body (see Chapter 26 ‘Cardiovascular disorders’, p. 192).
• proper function of the nervous system (see Chapter 31 ‘The nervous system’, p. 235).

• Copper

See Wilson’s disease (see Chapter 37 ‘Metabolic disorders’, p. 297).

• Homocysteine

This is now considered a biomarker for inadequate folate, vitamin B12 and to a lesser extent vitamin B6 status, as all these enzymes are involved in homocysteine metabolism (see Chapter 37 ‘Metabolic disorders’, p. 296). Blood for measuring serum homocysteine levels is taken after a 12-hour fast. Levels between 5 and 15 μmol/L indicate insufficiency.

• Liver Function Tests

The liver is responsible for a great variety of metabolic processes in the body. Liver function tests are never performed in isolation and are usually additional information to a case history, examination and other test results.

Alanine Aminotransferase or Alanine Transaminase (ALT)

This is also known as serum glutamic pyruvate transaminase (SGPT). ALT is produced in the cells of the liver. The level is abnormally raised when these cells have been inflamed or have died. The ALT leaks out of the cells into the bloodstream if there is cell damage. Any form of liver cell damage can cause raised ALT levels. The levels are not necessarily an indicator of the degree of damage. This test is the most sensitive marker for liver cell damage.

Aspartate Aminotransferase or Aspartate Transaminase (AST)

AST is also known as serum glutamic oxaloacetic transaminase (SGOT). This also indicates liver cell damage. It is not as specific for liver disease as ALT. It can become elevated in situations such as a myocardial infarction, where heart cells are damaged.

Alkaline Phosphatase (ALP)

• Is an enzyme that is produced by the bile ducts.
• Is also found in bone and the placenta.
• Renal or intestinal damage can also cause an increase and it is therefore not specific to the liver.
• A serological test, called ALP isoenzyme test, can be run to determine the origin of the alkaline phosphatase. If the gamma glutamyl transpeptidase (GGT) test and the other function tests such as bilirubin are abnormal then the liver is involved.

Gamma Glutamyl Transpeptidase (GGT)

• This enzyme is also associated with the bile ducts.
• It is largely used to confirm whether the alkaline phosphatase is from the liver.
• If the GGT is an isolated finding then there might be a rare form of liver disease.
• Medications can cause the GGT to be raised as can alcohol or other liver toxins.

• Bilirubin

• A major breakdown product of haemoglobin.
• Haemoglobin comes from the red cells that are about 120 days old and have become too fragile to function. Their cell membranes rupture and the released haemoglobin is phagocytosed by the tissue macrophages throughout the body.
• The bilirubin that eventually forms is released from the macrophages into the bloodstream and immediately binds with the albumin in the plasma and is transported around the body.
• This bound form of bilirubin is called free bilirubin.
• The free bilirubin eventually reaches the liver, where it is released from the plasma albumin.
• It then undergoes a process called conjugation to form conjugated bilirubin, which is excreted in the bile.
• Bilirubin is converted to urobilinogen in the small intestine. This highly soluble compound is reabsorbed by the small intestine wall back into the blood.
• The function of bile salts is to emulsify fat in the small intestine, thus giving the digestive enzymes a larger surface area to work on.

There are two reasons for an increase in total bilirubin:

• Haemolysis of red blood cells: with haemolytic jaundice there is no blockage of the bile ducts. The red blood cells are broken down faster than the end product can be excreted. The plasma concentration of free bilibrubin rises abnormally. There is no blockage of the bile ducts, so the concentration of urobilinogen in the blood also increases. In this case, the bilirubin is largely in the ‘free’ form.
• Obstructive jaundice: this is caused by obstruction of the bile ducts or liver disease. The ducts can be blocked by gallstones, by cancer or by damage to the liver cells. The free bilirubin enters the liver and is conjugated as normal but cannot enter the small intestine due to the blockage of the duct. The only route for the conjugated bilirubin is back into the bloodstream. This may be due to a congested bile duct rupturing and directly emptying its contents into the lymph system. The bilirubin in the plasma in this case is of the conjugated kind and not the ‘free’ form.

• Total Proteins (TP) or Total Serum Protein

Measures total amount of protein in the blood. There are two main types of protein in the blood: albumin and globulins.

Albumin

• This is the most common protein in the blood.
• It is synthesized by the liver.
• Can give an idea of how well the liver is synthesizing proteins and acts as a ‘marker’ protein.
• The test is a reliable and inexpensive way of assessing the degree of liver cell damage.
• Other tests and information have to be taken into account as malnutrition can also cause low albumin.

Globulins

• There are alpha, beta and gamma globulins.
• Some are part of the immune system (see Chapter 30 ‘Inflammation and the immune system’, p. 225) and so can be used to see if the patient is susceptible to infection.
• Others bind to iron (see Chapter 28 ‘Blood disorders’, p. 211) and so can be used to see if the patient is likely to have a rare blood disorder.

• Prothrombin Time (PT)

This gives an indication of the total quantity of prothrombin in the blood. The blood sample is prepared in a particular way so that the coagulation time can be measured. The normal prothrombin time is 10–15 seconds. This time is prolonged in patients with liver disease. This is not a specific test for liver dysfunction and should be used in conjunction with other liver tests.

• Platelet Count

See above.

• Efficiency of Liver Detoxification

This liver function test investigates the efficiency with which the liver can detoxify compounds. It is not the same as the liver function tests described above, which ascertains whether there has been destruction of the liver cells, but is a test of the efficiency of the detoxification pathways of the liver. The information gathered from this test will indicate to a practitioner the nutritional input and patient management that is required to improve the patient’s detoxification pathways.

The patient is loaded with small amounts of caffeine, aspirin and paracetamol. These are taken in the morning and the clearance rates are assessed from two saliva samples at a specified time. Urine samples are also taken over a specified period of time. The efficiency with which these substances are cleared from the system will dictate the efficiency of the liver’s detoxification efficiency:

• Low caffeine clearance indicates that phase I liver metabolism is not functioning efficiently enough.
• The efficiency with which the aspirin and paracetamol are handled indicates the efficiency of the phase II pathway.

• Blood Lipids

• Total cholesterol: high levels indicate a high risk of cardiovascular disease.
• High-density lipoproteins (HDL): high levels indicate a lower risk of cardiovascular disease.
• Low-density lipoproteins (LDL): high levels indicate a high risk of cardiovascular disease.
• Triglycerides: high levels are associated with cardiovascular disease or pancreatitis. Patients with syndrome X tend to have high triglyceride levels.

• Endocrine Tests

Thyroid Function Tests (see Chapter 37 ‘Metabolic diseases‘, p. 288)

The initial test used is for thyroid-stimulating hormone (TSH), which is deemed to be reliable because it does not fluctuate much on a daily basis. TSH is secreted from the pituitary gland; its production is controlled by a feedback system, which depends on the amount of thyroxine (T4) in the system. So TSH levels give an idea of how the function of the thyroid gland is perceived by the pituitary gland, and not by the peripheral tissues it has an action on. Thus, if the patient is known to have a pituitary problem, this test only gives a rough measure of thyroid output:

• Increased levels TSH 5 an effort to stimulate the thyroid gland 5 hypothyroidism.
• Decreased levels TSH 5 an effort to shut off the thyroid gland from producing too much thyroxine 5 hyperthyroidism.

T4 contains four iodine atoms. One atom is removed to form tri-iodothyronine (T3); so-called because it has three iodine atoms. The amount of T4 is controlled by TSH secreted by the pituitary. T4 enters the blood in two forms:

• Protein-bound T4: prevents T4 entering target tissues (see Chapter 16 ‘How do drugs get into cells?’, p. 125).
• Free T4: can enter target tissues. This is therefore the most important method of ascertaining how the thyroid is functioning.

By combining the results from the TSH and free T4 (FT4), it becomes possible to discern whether the thyroid problem is secondary to a pituitary problem or primary.

T3 is useful for hyperthyroidism tests but not used for hypothyroidism as this is the last test to become abnormal (Table 41.2).

Table 41.2 Possible results of thyroid function test (See also Chapter 37 ‘Metabolic diseases’, p. 288).

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Female Hormone Levels

These tend to be performed for infertility, menopause or as part of the examination of menstrual irregularity and include:

• Prolactin, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels – also found in men but for the purposes of this book are ignored.
• Infertility tests: see Chapter 38 ‘Reproductive hormones’ (p. 302).

• Urinalysis (Dip-Stick Testing)

• Urinalysis: reagent strips (known as ‘chemical stix’) are dipped into a urine sample. A colour reference chart on the side of the container denotes the results of the various tests. Urine samples are usually taken on a midstream sample to reduce any normal sediment present. Any sediment that is found can then be analysed for the presence of red and white blood cells, crystals, bacteria, etc. It is important to remember that some food stuffs, such as beetroot, will dye the urine red and that vitamin B2 (riboflavin) makes the urine turn bright yellow.
• pH: measures the acidity of the urine.
• Specific gravity: measures how concentrated the urine is, but there will be fluctuations depending on how hydrated the patient is.
• Glucose: there should be no glucose in the urine under normal circumstances. Glucose in the urine will result in a retest and in a blood test for glucose if this proves positive.
• Protein: no protein should be present in the urine normally. However, children or athletes under intensive training might have protein in their urine.
• Blood: no blood should be present in the urine under normal circumstances; female patients who are menstruating will have to be retested at another time as their sample might be contaminated. Blood can indicate trauma, infection, kidney stones or cancer of the bladder or kidney.
• Bilirubin: there should be no bilirubin in the urine, although this might be present if there is liver or gall bladder disease.
• Nitrates: should be negative; the presence of nitrates indicates a urinary tract infection.

• Stool Analysis

• Occult blood: if bleeding occurs high up enough in the intestine to be blended sufficiently with the stools, it will not be immediately noticeable. Can be used as a screen for colon cancer (see Chapter 35 ‘Gastrointestinal disorders’, p. 279).
• Parasites: the stool sample is examined for parasites, e.g. those found in tropical diseases, such as pinworm or giardiasis.
• Infection: the sample can be examined for bacteria or fungi.

Qualitative Analysis In Brief

Goldbeater’s Skin Test

A membrane prepared from the intestine of an ox behaves similarly to an untanned hide. The skin is soaked in 2% hydrochloric acid then rinsed with distilled water and put into the test solution for 5 minutes. The skin is then transferred to a 1% solution of ferrous sulphate. A brown or black colour occurs if tannins are present in the test solution.

Chromatography

This is used to separate compounds out of a mixture. The test compound is dissolved in a solvent and then passed through a stationary phase substance. This substance remains static and the dissolved compounds either move through or adhere to it. High-performance liquid chromatography is the most common type of chromatography used in the quality control of herbs. The groups of chemicals are forced through the stationary phase in a column at high pressure, to speed the process up. The points at which the various chemicals stop are analysed by computer. This enables manufacturers or scientists to quickly analyse plant chemicals and isolate them.

Spectrometry

An optical instrument is used to measure light of specific frequencies but varying intensity. This enables scientists to calculate the concentration of a particular compound in a test solution. The concentration of a particular compound in a chosen plant can then be determined.

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