Interpreting blood test results - Biochemistry

What is biochemistry?

The analysis of molecular components of bodily fluids (mainly serum and plasma) for diagnostic and therapeutic purposes.

What organ systems does biochemistry look at?

Proteins

Kidneys

Liver

Pancreas

Intestine

Muscles, incl. heart

In biochemistry, what do “total protein,” “albumin,” and “globulin” mean?

Total protein is albumin + globulins. Many analysers measure total protein and albumin, then calculate globulin as total protein minus albumin

Where are proteins predominantly synthesised?

In the liver. Except immunoglobulins which are produced by lymphocytes

Why are proteins clinically important?

Important for oncotic pressure and transport of other substances

What happens to protein concentration in the blood when dehydrated?

Increased albumin and globulin concentration (less water to dilute the blood)

What happens to protein concentration in the blood when malnourished?

Decreased albumin and globulin concentration (due to lowered liver function or losses e.g. diarrhoea, bleeding)

In which circumstances can the proteins albumin and globulin increase and decrease independent of each other?

Inflammation: Albumin decreases, globulins increase

Renal loss: Albumin (very small) is lost via kidney, globulins typically not

Lymphoid neoplasia: Only increases a selective immunoglobulin

Which values do you look at for kidney function?

Creatinine

Urea

SDMA (symmetric dimethylarginine)

What is the origin of creatinine and what can cause its levels to be low?

• Origin: It comes from physiologic muscle turnover.

• Low levels: Occur with decreased muscle mass.

How is urea produced and when might levels be low?

• Production: It is made in the liver from ammonium via the urea cycle, using protein catabolism from both exogenous (food) and endogenous (muscle) sources.

• Low levels: Occur with hepatic insufficiency.

How is SDMA (Symmetric Dimethylarginine) produced?

It is released into the blood circulation following the process of proteolysis. It has relatively constant production with little influencing factors

What is azotaemia and what physiological change does it indicate?

• Definition: An increase in creatinine and urea.

• Indication: A decrease in the glomerular filtration rate.

What is the primary cause of pre-renal azotaemia and what three things can make this happen?

• Primary Cause: Less blood flow to the kidney.

• Examples: Dehydration, shock and decreased cardiac output.

Differentiate between renal and postrenal azotaemia based on their causes.

• Renal: Caused by AKI (acute kidney injury) or CKD (chronic kidney disease).

• Post-renal: Caused by urinary tract obstruction or leakage into the body (e.g., bladder rupture).

What two factors must be assessed alongside azotaemia to ensure an accurate diagnosis?

1. Urine concentration.

2. Hydration status.

What is the purpose of doing a USG (urine specific gravity)

To assess the concentration ability of the renal tubular system

NEED TO ASK - HEALTHY USG

NEED TO ASK - HEALTHY USG

What are three examples of electrolytes?

Na⁺, Cl^-, K⁺