Introduction to Interpreting Clinical Tests

This set of flashcards covers key vocabulary and concepts related to the interpretation of clinical tests in medical contexts.

Aetiology

The study of the cause or origin of a disease.

Epidemiology

The branch of medicine that deals with the distribution and control of diseases.

Pathophysiology

The study of the disordered physiological processes associated with disease.

Therapeutic intervention

Treatment that aims to relieve or cure a disease.

Clinical examination

The process of examining a patient to determine their health status.

eGFR

Estimated Glomerular Filtration Rate, a test to measure kidney function.

Hyponatraemia

Condition where sodium levels in the blood are lower than normal.

Hyperkalaemia

Condition characterized by high levels of potassium in the blood.

Interpreting clinical tests

Analyzing lab results with consideration of clinical context and history.

Pharmaceutical care intervention

A strategy aimed at improving the effectiveness of drug therapy for a patient.

Biomarker

A biological molecule that indicates a condition or disease.

ICD

International Classification of Diseases, used for diagnosis coding.

Clinical context

The clinical background and situation accompanying a patient's data.

Monitoring efficacy

The process of assessing whether a treatment is effective.

Clinical decision-making

The process of making clinical decisions based on data and clinical judgement.

Incidental findings

Unexpected results found during medical testing that were unrelated to the original reason for the test.

What is the normal serum potassium range?

3.5–5.3 mmol/L

What serum potassium value is considered immediately dangerous?

>6.5 mmol/L

What is the commonest cause of hyperkalaemia?

Haemolysed blood sample

What is the primary concern in hyperkalaemia?

Cardiac arrhythmias and risk of sudden death

Name three acute treatments for hyperkalaemia.

Calcium gluconate; insulin+dextrose; nebulised salbutamol

What is the maximum IV potassium concentration for a peripheral line?

40 mmol in 1 L

In respiratory acidosis

does potassium rise or fall?

Which diuretics cause hypokalaemia?

Loop and thiazide diuretics

ECG change in hyperkalaemia?

Tall tented T waves → wide QRS → sine wave

Normal serum sodium range?

135–145 mmol/L

Hyponatraemia with dilute urine suggests what?

ADH is off → excess water intake

Hyponatraemia with concentrated urine suggests what?

ADH is on → SIADH or hypovolaemia

Why does a salty meal cause temporary hyponatraemia?

ADH release causes water retention

What does a high urea with normal creatinine suggest?

Upper GI bleed

Creatinine is a product of what tissue?

Muscle

Why can frail elderly patients have deceptively normal creatinine?

Low muscle mass → low creatinine

Why is eGFR often inaccurate in AKI?

Creatinine not at steady state

Which equation should be used for renal drug dosing?

Cockcroft–Gault

Name three causes of post-renal AKI.

Ureteric obstruction; enlarged prostate; obstruction of solitary kidney

Which condition can cause permanent moderate renal impairment despite mild symptoms?

Acute interstitial nephritis

Why is true anuria rare?

Requires both kidneys to fail simultaneously or obstruction of both

Normal serum calcium range?

2.2–2.6 mmol/L

Main causes of hypercalcaemia?

Primary hyperparathyroidism; malignancy

Symptoms of hypercalcaemia?

"Stones bones groans psychiatric overtones"

ECG change in hypercalcaemia?

Short QT interval

Why does immobilisation cause hypercalcaemia?

Increased bone resorption

What is the first question when LFTs are raised?

Hepatocellular vs cholestatic pattern?

When is serum sodium useless?

Reflects water balance only

What happens to potassium in respiratory acidosis?

Potassium rises

What is the danger of treating a false-positive high potassium?

Inducing dangerous hypokalaemia

Why is severe hypernatraemia dangerous?

Brain shrinkage → haemorrhage

Why does acidosis cause hyperkalaemia?

H+ enters cells and K+ shifts out

Why repeat a high potassium before treatment?

To exclude haemolysis

Name medications that raise potassium.

ACE inhibitors; ARBs; spironolactone; eplerenone; trimethoprim

Why does insulin lower potassium?

Stimulates Na/K ATPase → shift into cells

Why is salbutamol used in hyperkalaemia?

β2 effect increases K+ uptake into cells

What electrolyte abnormality requires correcting magnesium first?

Refractory hypokalaemia

Why does serum sodium reflect water balance not sodium balance?

ADH tightly regulates water

Main determinant of ADH release?

Serum osmolality

Why is urine sodium high in SIADH?

RAAS suppressed → sodium lost in urine

What is the neurological risk in acute severe hyponatraemia?

Cerebral oedema

What is the risk of correcting chronic hyponatraemia too fast?

Osmotic demyelination syndrome

Why does hypernatraemia always mean insufficient water?

Thirst mechanism prevents sodium rise

Where is ADH produced and released?

Produced in hypothalamus; released from posterior pituitary

Effect of ADH on kidney?

Inserts aquaporin-2 in collecting duct → water retention

Why does drinking too much water turn off ADH?

Low osmolality

When is creatinine a poor indicator of renal function?

Low muscle mass

Why does dehydration disproportionately raise urea?

ADH increases urea reabsorption

What two factors determine creatinine?

Kidney clearance + muscle mass

Why is creatinine more reliable than urea?

Urea influenced by many non-renal factors

Why GI bleeds raise urea not creatinine?

Digested blood increases protein load

Three categories of AKI?

Pre-renal; intrinsic; post-renal

What suggests pre-renal AKI?

High urea:creatinine + concentrated urine

Important bedside test for post-renal AKI?

Bladder scan

Renal cause of rapid AKI in older men?

Prostate obstruction

What kidney condition causes subtle but permanent damage?

Acute interstitial nephritis

Which hormone raises calcium?

PTH

Why does malignancy cause hypercalcaemia?

PTHrP or bone metastases

ECG change in hypocalcaemia?

Prolonged QT

Why does respiratory alkalosis cause hypocalcaemic symptoms?

More albumin-calcium binding

Which LFT abnormality suggests bone disease?

Isolated high ALP

Which LFT pattern suggests hepatocellular injury?

Raised ALT/AST

Why is ALP high in children?

Bone growth

What test differentiates bone vs liver ALP?

GGT

Effect of hyperventilation on K+?

Decreases

Which acid-base disturbance raises potassium?

Acidosis

Why do opioids accumulate in renal failure?

Active metabolites renally excreted

Two findings favouring SIADH over hypovolaemia?

Euvolaemia + high urine sodium

Why urine stays concentrated in SIADH?

ADH remains on

Why is sodium poor marker of dehydration?

Thirst maintains sodium

What counts as a clinical test?

BP; weight; height; cholesterol; glucose

Stage 3 key concept for interpreting tests?

Rate of change more important than one value

Which drug example teaches rate-of-change monitoring?

Atomoxetine

Why normal ≠ healthy?

Context varies (e.g. HR 120 normal in infants)

Which LFT matters for protein-bound drugs?

Albumin

What symptoms are associated with raised bilirubin?

Jaundice; pruritus; ascites

Normal urine production?

1–2 L per 24h

Why is Cockcroft–Gault still used?

Drug dosing and narrow-therapeutic-window drugs

Creatinine clearance

Severe renal impairment

CrCl 20–50 mL/min indicates what?

Mild renal impairment

Two causes of reduced urea?

Hepatic dysfunction; pregnancy; oedema; dialysis

Which recreational drug triggers uncontrollable thirst → hyponatraemia?

Ecstasy (MDMA)

One cause of hypernatraemia listed in PPT?

Drugs