The Three Major Stress Hormones: Adrenaline, Cortisol, Norepinephrine

Thanks to the work of our sympathetic nervous system, the "fight or flight" system that takes over when we're stressed, when you see your boss's name in your inbox late at night, your body reacts like there's a lion on the loose.

Behind the wide range of both physical and mental reactions to stress are a number of hormones that are in charge of adding fuel to the fire.

Adrenaline

What It Is: Commonly known as the fight or flight hormone, it is produced by the adrenal glands after receiving a message from the brain that a stressful situation has presented itself.

What It Does: Adrenaline, along with norepinephrine (more on that below), is largely

Preanalytical Variables : Controllable or uncontrollable (Part 3)

Standardization of specimen collection practices help reduce errors due to preanalytical variables.
 

• Major physiological variables include posture, prolonged bed rest, exercise, physical training,
• circadian variation and travel.
• Other physiological variables include diet, lifestyle, stimulants, drugs, herbal preparations,
• recreational drug ingestions etc.

Controllable Parameters

• Posture – Changes water and plasma protein distribution. Many hormones’ values are
• affected, some of them drastically. Related to that, electrolytes’ values also change.
• Prolonged bed rest – Fluid retention occurs and related changes occur. Ca, Na, K, PO4 , SO4 changes. Also enzymes and hormones.

Pre-analytical variables : Various types of Sample collection procedure in clinical laboratory (Part 2)

 Urine Collection

• Untimed, random specimens
• Pre-determined interval of time – 1, 4, or 24 hours\
• Clean, morning, fasting specimen – Preferred for most tests.
• Clean, timed specimen – Specific times of the day.
• Mid-stream specimen – Bladder disorders
• Double-voided specimen – GTT
• Metabolic disorders – Acute phase
• Catheter specimen – Microbiological examination in critically ill

Pre-Analytical variables: Sample Collection (Part 1)

Errors during collection, processing and transport of biological specimens are common (Ref: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 4th Ed).

• Common samples collected are
• Whole blood
• Serum
• Plasma
• Saliva
• Pleural, pericardial, ascitic fluid
• Various types of solid tissues
• Spinal, Synovial, amniotic fluid.

 Blood Collection

• Sources – Artery, veins, capillaries
• Venous blood – Venipuncture
• Arterial blood puncture – Arterial blood gas analysis
• Capillaries – Skin puncture, in young children and for point-of-care testing

Cancer gene testing : BRCA1 and BRCA2 genes

Explaining Jolie's cancer:

News of Angelina Jolie's decision to undergo a prophylactic double mastectomy has instantly increased awareness of hereditary forms of cancer caused by mutations in the BRCA1 and BRCA2 genes.

Fig. Actress Angelina Jolie

While the BRCA1 and BRCA2 genes were discovered in the mid-1990s, genetic testing for the genes is increasingly available. Jolie's case highlights the importance of knowing one's family history and learning one's cancer risks in order to address them proactively.

Everyone has the BRCA1 and BRCA2 genes. We have two copies of each gene and get one each from our mother and father. They play a role in protecting the body against the development of cancer.

Individuals with mutations in either of these genes have increased cancer risks, most notably for breast and ovarian cancer. Individuals with mutations in BRCA1 and BRCA2 benefit from tailored management aimed at reducing cancer risks and detecting cancers early when they are most treatable.

Interpreting and Correlating Abnormal Laboratory Values : Cardiac Function Tests

Diagnosis of Myocardial Infarction (MI) and Acute Coronary Syndrome

Fig. Getting MI attack

Since acute MI (AMI) requires rapid and accurate diagnosis, especially now that new treatment options with thrombolytic agents are available, the clinical laboratory has been called upon to provide serum diagnostic tests that can make this diagnosis at an early stage. Until recently, laboratory diagnosis was based on serial determinations of the MB fraction of creatine phosphokinase (CK-MB); confirmation of the diagnosis was provided by the so-called ‘flipped ratio’ of the isozymes of lactate dehydrogenase (LD) 24-36 hours after the initial acute event and/or by observation of the characteristic time courses for elevations of the three enzymes, CK, aspartate aminotransferase (AST) and LD.

Interpreting and Correlating Abnormal Laboratory Values : Liver Function Tests

The most common liver test abnormalities can be summarized to a set of six conditions as in Table 1. The principles for these patterns are explained as follows.

1.

All acute injuries and/or necrotic lesions in the liver primarily cause a marked rise in the levels of the aminotransferases, aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Cell injury and necrosis also cause the rise of other enzymes such as lactate dehydrogenase (LD). These include acute hepatitis

Interpreting and Correlating Abnormal Laboratory Values : Electrolyte Abnormalities

Electrolyte Abnormalities

Hyponatremia

The four most common causes of hyponatremia are given in Table 1 (See below), together with a fifth, rare, cause, Bartter's syndrome. A sixth, metabolic cause, diabetes mellitus, is also presented in this table. In all forms of hyponatremia, the chloride ion concentration is also generally low since chloride is the chief counter-ion for sodium.

Interpreting and Correlating Abnormal Laboratory Values : Glucose Abnormalities

The major purpose of performing analyte determinations in the clinical laboratory is to aid in the diagnosis and management of patients with disease and individuals in health assessment. In this regard, the clinical pathologist/Clinical Biochemist/Clinical Microbiologist are often called upon as a consultant to explain abnormal laboratory values, especially those that do not seem to correlate with one another, and to recommend or even to order laboratory tests that may lead to the correct diagnosis in the work-up of patients for particular medical problems.

POCT : Point of Care testing - Introduction, Utility and Management

Point-of-care testing (POCT) is an emerging concept in laboratory medicine and has attracted considerable interest in the medical literature. Recent experience has revealed a variety of applications for these new technologies in

Relation between HbA1c and Estimated Average Glucose (eAG)

Why is relating HbA1c to glucose important?

We are frequently asked about the relationship between HbA1c and plasma glucose levels. Many patients with diabetes mellitus now perform self-monitoring of blood glucose (SMBG) in the home setting, and understanding the relationship between HbA1c and glucose can be useful in setting goals for day-to-day testing.

Hormones and Body Weight

Excessive intake of calories in relation to energy expenditure over a long period of time results in body weight gain.

A complex physiologic system regulates energy homeostasis by integrating signals from peripheral organs with central coordination in the brain. The hypothalamus functions as the main cerebral center in which these signals converge.

HORMONES REGULATING MINERAL METABOLISM

REGULATION OF MINERAL METABOLISM:

PTH and 1, 25-dihydroxyvitamin D are the primary hormones regulating bone and mineral metabolism. Physiological role of calcitonin has not yet been established. PTHrP is the principal mediator of humoral hypercalcemia of malignancy.

PARATHYROID HORMONE

PTH (chromosome 11) is synthesized and secreted by parathyroid glands located posterior to thyroid gland. The glands consist of chief and oxyphil cells; the chief cells synthesize, store, and secrete PTH. It is cleared by liver and kidney. PTH acts directly on bone and kidney, and indirectly on intestine to regulate concentration of calcium and phosphate in plasma.

Phosphate: Introduction, Clinical significance and measurement

An adult contains 600 g of phosphorus in inorganic and organic phosphates, of which about 85% is in skeleton and rest in soft tissue and extracellular fluid. Though plasma has both organic and inorganic phosphate but inorganic phosphate (H₂PO₄^- and HPO₄^2-) is measured. Approximately 10% is protein bound and 35% complexed with sodium, calcium, magnesium; and remainder 55% is free. The organic phosphates are located within the cell of blood.

Inorganic phosphate is a major component of hydroxyapatite in bone and is the source of intracellular and extracellular pool. Organic phosphate in cells is found to be incorporated into nucleic acid, phospholipids, phosphoproteins and ATP, GTP, Creatine phosphate, etc. Phosphate is important for activity of adenylate cyclase, 25-hydroxy vitamin D-1α-hydroxylase and those involved in 2, 3-diphosphoglycerate.

Calcium : Introduction, clinical significance and measurement

About 99% of calcium occurs in bone, along with calcium 85% of phosphate and 55% magnesium. The concentration of these minerals depends on net effect of bone mineralization, intestinal absorption and renal excretion. PTH and 1, 25-dihydroxyvitamin D are the principle hormones regulating these three processes.

Urine Sodium and Fractional excretion of Sodium (FENa)

Urine Sodium and FENa:

Urine sodium is the concentration of sodium in the urine. Remember that the normal value for blood sodium is 135-145 mmol/litre. Note that the range of sodium in urine is far greater than the range in the blood.

The reference range varies according to age and sex. If also depends upon the hydration state of the person. 

  40-220 mmol/L (For male)
27-287 mmol/L (For female)

For children aged 6-10 Year:
41-115 (For male)
20-69 (For female)

Quality control in Biochemistry laboratory

Quality Assurance in the biochemistry laboratory is intended to ensure the reliability of the laboratory tests. The objective of quality assurance is to achieve reliable test results by 

• Accuracy
• Precision

Accuracy

This refers to the closeness of the estimated value to that considered to be true. Accuracy can, as a rule, be checked only by the use of reference materials which have been assayed by reference methods.

Precision

This refers to the responsibility of the result, but a test can be precise without being accurate. Precision can be controlled by replicate tests and by repeated tests on previously measured specimens. And the test result or value which we get should be closer to the previous one.

Inaccuracy and/or imprecision occur as a result of using unreliable standards or reagents ,incorrect instrument calibration, or poor technique.eg consistently faulty dilution or the use of a method that gives a reaction that is incomplete or not specific for the test.

First of all, Edward Demming gave the idea about quality control. According to him,

Improved quality=increased productivity at lower cost.

This can be done by

1. Eliminating rework
2. Save time
3. Save labour
4. Save material e.g. reagent, specimen etc.
5. Patient care.

Quality Assurance Programme Includes

• Internal quality control (IQC)
• External quality assessment (EQC)
• Proficiency surveillance
• Standardization

How to do Urine Pregnancy Test

Urine Pregnancy Test

(Human chorionic gonodotropin test)

The hCG one step test is used for the qualitative detection of human chorionic gonodotropin in urine.

Principle

Fig. Pregnancy test strips

The hCG one step pregnancy test is a rapid chromatographic immunoassay for the qualitative detection of human chorionic gonodotropin in urine to aid in the early detection of pregnancy. The test device consists of two lines for the result indication, the test line and the control line. The test line consists of combination of antibodies including monoclonal hCG antibody where as the control line consist of goat polyclonal antibodies and colloidal gold particles. When urine specimen is added in the wall of test device the specimen migrates along the membrane to react with the colored reconjugate via capillary action and form the colored line. Presence of colored line indicates positive result where as absence of colored line indicates negative result.

Reagents

The test device consists anti hCG particles and anti hCG coated on membrane.

Dipstick method for Urinalysis (MULTISTIX METHOD)

DIPSTICK METHOD OF URINALYSIS

Multistix reagent strip method

Multistix reagents are clear plastic strips. Seven different reagent areas are affixed on the strip. These different cellulose areas are impregnated with specific testing chemicals according to the test which reacts with specific substances present in urine by changing the color. Color change chart is observed and compared to the color chart for the presence of abnormal levels of substances .Special care in their use is required to prevent inaccurate results and confirmation of quantitative test is appropriate if the results from dipstick testing reveal abnormalities.

The various determinations done by multistix are

pH, Specific Gravity, Glucose, Protein, Ketones, Urobilinogen, Blood, Bilirubin

Fig. Multiple strip for Urinalysis and their interpretaiton

The reagent strips are also available for only one or two tests such as glucose, glucose and protein, glucose and ketones.

Urinalysis : Chemical Examination

Chemical Examination of Urine

The routine analysis of urine includes chemical test for protein, glucose, ketone bodies, occult blood, bile salts, bile pigments and urobilinogen. 

Proteins in urine

Urine normally contains only a scant amount of protein which derives both from blood and urinary tract itself. Mainly albumin is filtered from nephrons due to low molecular weight others are reabsorbed by renal tubules. Other protein includes serum or plasma globulin, mucus or mucin, hemoglobin, bence jones protein.

Determination of protein in urine

Principle

All the methods are based on the principle of precipitation of protein by chemical agents or coagulation by heat.