Category
Investigations
Blood tests, imaging and clinical measurements.
Subcategories
Full blood count, blood film, coagulation and haematinics.
Biochemistry and ElectrolytesUrea and electrolytes, liver function, calcium and the gaps.
Blood Gases and Acid BaseArterial blood gas interpretation and acid base disorders.
ECG InterpretationRate, rhythm, axis, intervals and the lead territories.
Imaging InterpretationSystematic review of radiographs and choosing the right test.
Microbiology and SerologyCultures, sensitivities, stains and serological patterns.
Body Fluids and UrinalysisUrine, cerebrospinal, pleural, ascitic and joint fluid analysis.
Lung Function TestsSpirometry, peak flow, lung volumes and transfer factor.
Endocrine and Dynamic TestingThyroid function, suppression and stimulation tests.
Cardiac and Vascular TestingEchocardiography, exercise testing and ambulatory monitoring.
Genetics and Tissue DiagnosisBiopsy, cytology, immunohistochemistry and genetic testing.
Test Interpretation and StatisticsSensitivity, specificity, predictive values and screening.
Entries in Investigations
Bowel gas pattern, then solid organs, bones and calcification
A memory aid for reading a plain abdominal radiograph.
Arterial blood gas
A blood test used to assess oxygenation, carbon dioxide and acid-base status.
Respiratory Opposite, Metabolic Equal
A mnemonic to remember the relationship between pH and primary values in acid-base disorders.
Check pH, then carbon dioxide, then bicarbonate, then compensation, then the anion gap
A memory aid for a systematic approach to blood gas interpretation.
Staged by creatinine rise or urine output, classified as pre-renal, renal or post-renal
A memory aid for the stages of acute kidney injury and its causes.
Alanine aminotransferase
A liver-associated enzyme measured in liver function testing.
Daytime average over at least 14 measurements, with lower thresholds
A memory aid for the use and thresholds of ambulatory blood pressure monitoring.
Match the monitoring duration to the frequency of the symptoms
A memory aid for choosing the right rhythm monitoring device.
Lipase is more sensitive and specific and stays raised longer
A memory aid for interpreting pancreatic enzymes.
Microcytic, normocytic and macrocytic, each with a short differential
A memory aid for classifying anaemia by red cell size.
Sodium minus chloride and bicarbonate, normally 8 to 16 mmol per litre
A memory aid for calculating and interpreting the anion gap.
Combined test, quadruple test, anomaly scan and infectious disease screening
A memory aid for the antenatal screening programme and its tests.
Susceptible, intermediate or resistant, defined against a breakpoint
A memory aid for reading a sensitivity report and the resistance mechanisms behind it.
Oxygenation first, then pH, then carbon dioxide, then bicarbonate
A memory aid for the order in which to read an arterial blood gas.
SAAG separates portal hypertension from everything else
A memory aid for the serum ascites albumin gradient and ascitic tap.
Aspartate aminotransferase
An enzyme found in liver, muscle and other tissues.
Antinuclear antibody first, then the specific antibodies
A memory aid for which autoantibody points to which disease.
Serum levels, then the metabolites, then the cause
A memory aid for investigating suspected B12 and folate deficiency.
More tissue gives more information but carries more risk
A memory aid for choosing between fine needle aspiration, core and excision biopsy.
Two sets, separate sites, adequate volume, before antibiotics
A memory aid for taking and interpreting blood cultures.
Each morphological abnormality points to a specific diagnosis
A memory aid for the diagnostic features on a blood film.
WiLLiaM MaRRoW: W in V1 and M in V6 is left, M in V1 and W in V6 is right
A mnemonic for telling left from right bundle branch block.
Correct for albumin, then use the parathyroid hormone
A memory aid for correcting calcium and working out the cause of an abnormal result.
Both positive is normal; leads pointing away from each other indicate deviation
A memory aid for working out the cardiac axis from leads I and aVF.
Right border is right atrium; left border is aortic knuckle, pulmonary trunk, left atrial appendage and left ventricle
A memory aid for which chambers form the cardiac silhouette on a chest radiograph.
CT for the arteries, MRI for the muscle
A memory aid for when to use cardiac CT and when to use cardiac MRI.
Reduced production, increased destruction, sequestration or spurious
A memory aid for classifying a low platelet count.
Cells, protein, glucose and appearance distinguish the meningitides
A memory aid for interpreting a lumbar puncture result.
ABCDE: Airway, Breathing, Circulation, Diaphragm, Everything else
A mnemonic for reviewing a chest radiograph in order.
Radiation, availability, contrast risk and what the question is
A memory aid for selecting the right first line imaging test.
PT tests the extrinsic pathway, APTT the intrinsic, both the common
A memory aid for interpreting prothrombin time and APTT together.
A pulse oximeter reads two wavelengths and can be badly misled
A memory aid for carboxyhaemoglobin, methaemoglobin and the pulse oximeter's blind spots.
Extrinsic measured by prothrombin time, intrinsic by APTT
A memory aid for the intrinsic, extrinsic and common coagulation pathways.
Tissue transglutaminase IgA with a total IgA, on a gluten containing diet
A memory aid for testing for coeliac disease.
Predictable formulae reveal whether a second disorder is present
A memory aid for the expected compensation in each acid-base disorder.
Renal function, allergy, thyroid and metformin
A memory aid for the risks of iodinated and gadolinium contrast.
C-reactive protein
An inflammatory marker measured in blood tests.
A halo ring on gauze or sheet, CSF mixed with blood, a telltale feat
Mnemonic for testing suspected cerebrospinal fluid leak from the nose.
Immediate scanning criteria and the one hour and eight hour rules
A memory aid for who needs a CT head after a head injury.
Cytology examines individual cells; histology examines tissue architecture
A memory aid for the difference between cytology and histology.
A rule out test only, applied after a clinical probability score
A memory aid for when a D-dimer is useful and when it is not.
Confirm cortisol excess, then localise with ACTH and high dose suppression
A memory aid for investigating suspected Cushing's syndrome.
HbA1c, fasting glucose, random glucose and the tolerance test
A memory aid for the diagnostic thresholds for diabetes.
Direct detects antibody on the cells, indirect detects antibody in the plasma
A memory aid for the Coombs tests and the causes of a positive result.
Widespread activation of coagulation consumes factors and platelets, causing both thrombosis and bleeding
A memory aid for the mechanism and results in DIC.
Electrocardiogram
A recording of the heart’s electrical activity over time.
II, III and aVF inferior; V1 to V4 anterior; I, aVL, V5 and V6 lateral
A memory aid for which ECG leads look at which part of the heart.
Rate, rhythm, axis, intervals, then the waves in every lead
A memory aid for reading an ECG systematically.
P atrial depolarisation, QRS ventricular depolarisation, T ventricular repolarisation
A memory aid for what each ECG wave and interval represents.
Parasternal, apical and subcostal windows, transthoracic or transoesophageal
A memory aid for the standard echocardiographic views and what they answer.
Biconcave anucleate discs with central pallor, and anucleate platelet fragments
A memory aid for the normal appearance of red cells and platelets.
CRP rises and falls fast; ESR is slow and influenced by many factors
A memory aid for choosing between the two inflammatory markers.
Graded exercise with continuous ECG, looking for ischaemic change
A memory aid for the use, endpoints and limits of exercise ECG testing.
Full blood count
A common blood test measuring red cells, white cells and platelets.
Scooped expiratory limb in obstruction; flattening indicates large airway obstruction
A memory aid for interpreting the shape of the flow-volume loop.
Below 1 per cent suggests prerenal; above 2 per cent suggests tubular injury
A memory aid for using FENa to distinguish prerenal from intrinsic renal failure.
A marker of eosinophilic airway inflammation
A memory aid for the use of FeNO in diagnosing asthma.
Margins, tissue identification, and confirming malignancy during surgery
A memory aid for when an intraoperative frozen section is used.
Three cell lines, then the indices, then the film
A memory aid for reading a full blood count systematically.
Dominant appears in every generation; recessive skips; X-linked spares father to son
A memory aid for recognising modes of inheritance from a pedigree.
Resolution rises from whole chromosome to single base
A memory aid for choosing between karyotype, FISH, array and sequencing.
Glomerular filtration rate
A measure of kidney filtration function.
Colour, shape and arrangement narrow the organism quickly
A memory aid for identifying organisms from the Gram stain.
Group and save identifies the blood type; crossmatch reserves specific units
A memory aid for pre-transfusion testing and the safety rules.
Raised reticulocytes, bilirubin and LDH with low haptoglobin
A memory aid for the markers of haemolysis.
Glycated haemoglobin
A blood marker reflecting average blood glucose over roughly the previous two to three months.
First degree long PR, second degree some dropped beats, third degree complete dissociation
A memory aid for the degrees of atrioventricular block.
Surface antigen means infection, surface antibody means protection
A memory aid for interpreting the hepatitis B serological markers.
MUDPILES or GOLDMARK for the unmeasured anions
A mnemonic for the causes of a raised anion gap metabolic acidosis.
The left hilum is normally higher than the right, never lower
A memory aid for the normal position of the lung hila on a chest film.
Fourth generation antigen and antibody test, negative from 45 days
A memory aid for the HIV test, its window period and the monitoring markers.
Check osmolality, then volume status, then urine sodium
A memory aid for the stepwise assessment of hyponatraemia.
Immunohistochemistry
A laboratory technique using antibodies to detect antigens in tissue sections.
Antibodies against lineage-specific proteins identify a tumour's origin
A memory aid for the immunohistochemical markers identifying tissue lineage.
Incidentaloma, cascade and overdiagnosis
A memory aid for the harms of testing and how to manage an incidental finding.
Ferritin low in deficiency, normal or high in chronic disease
A memory aid for distinguishing iron deficiency from anaemia of chronic disease.
Type A from hypoperfusion, type B without it
A memory aid for interpreting a raised lactate.
Type A from hypoperfusion, type B without hypoxia
A memory aid for the two types of lactic acidosis.
Lactate dehydrogenase
An enzyme involved in the conversion between lactate and pyruvate.
Every device has a correct position and a characteristic malposition
A memory aid for checking the position of lines and tubes on a film.
Transaminases versus alkaline phosphatase and gamma GT
A memory aid for distinguishing hepatitic from cholestatic liver tests.
Transaminases indicate hepatocellular injury; ALP and GGT indicate cholestasis
A memory aid for interpreting the liver enzyme pattern.
Four volumes combining into four capacities
A memory aid for the lung volumes and which cannot be measured by spirometry.
Testing that determines which targeted treatment will work
A memory aid for the predictive biomarkers tested on tumour tissue.
CRAB: Calcium raised, Renal failure, Anaemia, Bone lesions
A mnemonic for the clinical features of multiple myeloma.
Width tells you where it starts, regularity tells you which one
A memory aid for classifying a tachycardia by QRS width and regularity.
Released by stretched myocardium; they oppose the renin-angiotensin system
A memory aid for the actions of atrial and brain natriuretic peptide.
Nine conditions in the UK programme, taken at day 5
A memory aid for the conditions detected on the newborn blood spot.
NNT is the reciprocal of the absolute risk reduction
A memory aid for absolute and relative risk and the number needed to treat.
Measured minus calculated osmolality, raised by unmeasured osmoles
A memory aid for using the osmolar gap in poisoning.
A p value measures compatibility with the null hypothesis, not the size of an effect
A memory aid for what a p value does and does not tell you.
Effort dependent, compared with predicted or personal best
A memory aid for using and interpreting peak flow.
Exudate or transudate first, then the specific tests
A memory aid for Light's criteria and the pleural fluid tests.
Predictive values answer the clinician's question but depend on prevalence
A memory aid for why the same test means different things in different populations.
Urine hCG for the question, serum hCG for the trend
A memory aid for interpreting human chorionic gonadotrophin.
Procalcitonin rises in bacterial infection and falls quickly with treatment
A memory aid for the biomarkers used to distinguish bacterial infection.
Two wavelengths distinguish oxyhaemoglobin from deoxyhaemoglobin in pulsatile blood
A memory aid for how pulse oximetry works and when it misleads.
Low potassium, magnesium and calcium, plus many drugs, prolong the QT interval
A memory aid for the causes of QT prolongation.
Muscle injury from any cause, with rhabdomyolysis at the extreme
A memory aid for the causes of a raised creatine kinase.
Reference ranges are defined statistically, not clinically
A memory aid for why so many normal people have an abnormal test result.
Type 1 distal, type 2 proximal, type 4 hypoaldosteronism
A memory aid for the types of renal tubular acidosis.
Anything reducing alveolar ventilation, from brain to alveolus
A memory aid for the causes of carbon dioxide retention.
Hypoxia, central stimulation, lung disease, drugs and anxiety
A memory aid for the causes of hyperventilation.
The condition, the test, the treatment and the programme
A memory aid for the Wilson and Jungner criteria for screening.
SnNout and SpPin
A mnemonic for what sensitivity and specificity mean and when to use each.
Measure cortisol before and after synthetic ACTH
A memory aid for the test of adrenal reserve.
Left ventricular hypertrophy criteria, and the causes of small complexes
A memory aid for high and low voltage on the ECG.
Obstructive lowers the ratio; restrictive lowers both values proportionately
A memory aid for distinguishing obstructive from restrictive spirometry.
Elevation suggests transmural injury; depression suggests subendocardial ischaemia
A memory aid for the significance of ST segment shift.
Culture, toxin, antigen, calprotectin and elastase answer different questions
A memory aid for choosing the right stool test.
Appearance, cell count, crystals and Gram stain
A memory aid for interpreting a joint aspirate.
Narrow therapeutic index drugs where effect cannot be measured directly
A memory aid for which drugs need level monitoring and when to sample.
Factor V Leiden is commonest inherited; antiphospholipid syndrome commonest acquired
A memory aid for inherited and acquired thrombophilia.
Timing, binding proteins, assay interference and acute illness all distort results
A memory aid for the common traps in endocrine biochemistry.
TSH is the most sensitive marker, moving before free T4 changes
A memory aid for interpreting thyroid function tests.
TLCO measures diffusion; KCO corrects it for the volume available
A memory aid for interpreting the gas transfer factor.
A marker of myocardial injury, not of myocardial infarction
A memory aid for interpreting a raised troponin.
Smear, culture and NAAT for active disease; Mantoux and IGRA for latent
A memory aid for the tests used in latent and active tuberculosis.
Most are for monitoring rather than diagnosis or screening
A memory aid for the common tumour markers and their uses.
Stage is how far it has spread; grade is how abnormal it looks
A memory aid for the difference between stage and grade.
Spot ratios have replaced timed collections for most purposes
A memory aid for when a timed collection is needed and when a spot ratio suffices.
Type 1 is a gas exchange problem, type 2 a ventilation problem
A memory aid for classifying respiratory failure and its causes.
Sodium, potassium, urea, creatinine and bicarbonate, read together
A memory aid for reading the urea and electrolytes systematically.
Blood, protein, leucocytes, nitrites, glucose and ketones
A memory aid for reading a urine dipstick and microscopy.
Deprive water, measure urine osmolality, then give desmopressin
A memory aid for interpreting the water deprivation test.
Neutrophils, lymphocytes, eosinophils, monocytes and basophils
A memory aid for what each raised or low white cell line indicates.