What the ACEM Primary assesses
The ACEM Primary Examination is a pre-Fellowship assessment of foundational sciences and their application to emergency medicine. It typically includes written components and structured oral or viva-style assessment. Candidates may need to explain mechanisms, interpret data and apply core principles to acute presentations under time pressure.
That description tells you how to prepare, but it does not establish exact paper formats, timings or rules. Check the current ACEM website and candidate information for those details, including any changes that apply to your sitting. Do not build your preparation around assumed question counts or timings.
The transferable task is to give a concise, accurate explanation and connect the science to a clinical decision. A list of facts is not enough if you cannot explain what causes a change, interpret the values in front of you, or say why the mechanism matters in an emergency setting.
Start with a board built from your own material
Collect the notes you already rely on: lecture slides, textbooks or course notes, annotated PDFs, and clear photographs of handwritten pages. Organise them into a revision board with sections that match the way you need to retrieve knowledge. For example: cardiovascular physiology, respiratory physiology, acid–base interpretation, pharmacology and cellular or tissue injury.
Keep each section small enough to test. A page headed “renal physiology” is too broad to review well; split it into filtration, tubular handling, regulation and clinical consequences. Include the original source or page reference in your own notes so you can check a disputed detail rather than memorising an error.
A MySummaries board on acid–base interpretation could look like this:
- Acidaemia: arterial pH <7.35
- Alkalaemia: arterial pH >7.45
- pH describes the blood state; it does not identify the primary process
- For metabolic acidosis: expected PaCO₂ (mmHg) ≈ 1.5 × HCO₃⁻ + 8 ± 2
- If the measured PaCO₂ is outside the expected range, consider an additional respiratory disorder
- Respiratory: PaCO₂ changes in the direction that explains the pH
- Metabolic: HCO₃⁻ changes in the direction that explains the pH
- Check whether a second process is present
- Check the clinical context, oxygenation, lactate, glucose, ketones and renal function as indicated
- A near-normal pH does not exclude a mixed disorder
Without potassium: AG = Na⁺ − (Cl⁻ + HCO₃⁻). Interpret against the laboratory reference interval and albumin; low albumin can conceal an elevated gap.
Use sections to hold examinable relationships, not just topic labels. For every formula, keep the units beside it and practise using values in those units. If a formula uses mmHg, do not substitute a value recorded in kPa without converting it. Record important caveats in the same section as the rule they qualify.
Build a short core checklist
Make a separate “must not miss” list for each major topic. It should be short enough to rehearse from memory, but specific enough to catch common errors: definitions, units, formulae, thresholds and the clinical implication. Check numerical facts against a reliable source and the material you are using for the examination; local laboratory ranges and clinical protocols can differ.
For acid–base work, a MySummaries core checklist might be:
Test the checklist both ways. First, cover the explanation and retrieve it from the heading. Then start with a clinical finding—such as a raised anion gap—and work back to the mechanisms and likely causes. That second direction helps you apply facts rather than merely recognise familiar wording.
Turn each section into retrieval practice
Use flashcards for single, assessable facts: one definition, relationship, equation or mechanism per card. Avoid cards that ask for an entire topic, since a vague answer can feel complete when important details are missing. Make the question specific enough that you can judge whether your answer was correct.
After answering, grade honestly. If you recalled the formula but forgot the units, that is not a fully correct response. If you knew the direction of a change but could not explain why, mark it for another review. Spaced repetition is most useful when the grade reflects what you actually retrieved, not what looks familiar on the screen.
Pair cards with worked applications. For example, calculate the anion gap from an ABG and chemistry panel, then decide whether respiratory compensation is appropriate. Explain each step aloud or in a few written lines. This exposes gaps that isolated fact cards will not find.
Practise oral answers as structured explanations
For viva-style practice, answer in a stable order: define the problem, identify the key mechanism, interpret the data, then link it to emergency care and safety. Lead with what matters most. If the question gives a patient, state immediate concerns before adding less urgent detail. Do not recite every cause you can remember; prioritise and justify the leading possibilities.
The examiner emphasis supplied for ACEM Primary preparation includes clear structure, mechanistic understanding, accurate definitions and units, clinical application, safety-first reasoning and concise answers. Practise stopping when you have answered the question. If the examiner asks a follow-up, respond to that point rather than restarting your whole explanation.
A MySummaries oral practice station can show how a response is assessed by the platform’s examiner persona. Its score is practice feedback, not an official ACEM mark or marking scheme. The three-minute target below is a practice target, not a statement about examination timing.
Examiner
A patient with suspected diabetic ketoacidosis has pH 7.18, PaCO₂ 2.4 kPa, HCO₃⁻ 7 mmol/L, sodium 132 mmol/L and chloride 100 mmol/L. Interpret the acid–base findings and explain the key physiological and emergency-care implications.
You identified the primary disorder early, but delayed the immediate safety implications.
ImproveState the acid–base diagnosis first, then prioritise potassium and clinical stability.
The high-anion-gap metabolic acidosis was recognised; the calculation and units needed clearer signposting.
ImproveShow 132 − (100 + 7) = 25 mmol/L, then qualify the result against albumin and the local range.
You linked the likely ketoacidosis to acute care but did not state why a high serum potassium can be misleading.
ImproveExplain that total-body potassium may be depleted despite an elevated serum concentration.
You connected ketone accumulation with acidosis but could explain the respiratory response more explicitly.
ImproveRelate metabolic acidosis to compensatory increased ventilation and lower PaCO₂.
You interpreted pH and bicarbonate but did not compare PaCO₂ with expected compensation.
ImproveConvert 2.4 kPa to about 18 mmHg; Winter's formula gives about 18.5 ± 2 mmHg.
The answer was understandable but repeated the diagnosis before reaching the clinical implications.
ImproveUse one pass through diagnosis, calculation, mechanism and safety.
A strong answerThis is a primary metabolic acidosis with acidemia; the anion gap is 132 − (100 + 7), or 25 mmol/L, which is raised against many laboratory ranges and should be interpreted with albumin. In suspected DKA, ketone accumulation is a likely cause, but I would check the clinical context and relevant investigations. Winter's formula gives an expected PaCO₂ of about 18.5 ± 2 mmHg, approximately 2.5 ± 0.3 kPa; the measured 2.4 kPa is broadly consistent with respiratory compensation. A high serum potassium does not exclude total-body potassium depletion, and insulin treatment can lower serum potassium. I would prioritise clinical stability and potassium monitoring, following the local DKA protocol.
That is a MySummaries station, filled with ACEM Primary material. Yours is written from your own notes. Start free
Review feedback by category, not just by total score. A weak interpretation of values needs calculation practice; a weak clinical link needs cases; an unclear answer needs timed speaking practice with a fixed structure. Keep one correction for the next attempt, rather than trying to change everything at once.
Use short audio reviews to revisit mechanisms
Audio is useful when you need to revisit a mechanism away from your desk, but it should not replace active retrieval. Listen once for the causal chain, then pause and reproduce it from memory. Return to the board when you cannot explain a step or when the recording conflicts with your source notes.
A MySummaries lecture generated from the same board could read back the topic in an examiner-style voice:
Transcript · tap any word to jump there
Start with the pH. A pH of 7.18 is acidemia, but that label alone does not tell us why the pH is low. Bicarbonate is 7 millimoles per litre, so the primary process is metabolic acidosis. Next calculate the anion gap: sodium minus chloride plus bicarbonate in brackets. Here that is 132 minus 107, giving 25 millimoles per litre. Compare that with the laboratory's reference interval and consider albumin, because a low albumin can make an elevated gap less obvious.
Now ask whether ventilation is compensating appropriately. Winter's formula estimates expected PaCO₂ in millimetres of mercury: 1.5 times bicarbonate, plus 8, with a range of 2 either side. For bicarbonate 7, that is about 18.5, plus or minus 2 millimetres of mercury. The measured PaCO₂ is 2.4 kilopascals, approximately 18 millimetres of mercury, so it is broadly within the expected range. State the units and the conclusion; do not simply say that the gases are compensated.
In a patient with suspected DKA, ketone accumulation can account for a high-gap acidosis, but the result must be interpreted with the clinical picture. A raised serum potassium does not mean potassium stores are adequate: total-body potassium may be depleted, and insulin can shift potassium into cells. The emergency-care link is therefore to assess stability, interpret the full clinical picture and monitor potassium in line with the local protocol.
A repeatable weekly cycle
Start each week by choosing a small number of board sections, based on your weakest retrieval and the material you still need to cover. Use a cycle like this, adjusting the session length to your schedule:
- Session 1 — 45 minutes: review one section of source notes and write a compact explanation of its mechanisms.
- Session 2 — 30 minutes: complete due flashcards; record cards you missed and correct the underlying note.
- Session 3 — 45 minutes: work through a data interpretation problem, showing units, calculations and clinical meaning.
- Session 4 — 30 minutes: answer one viva-style prompt aloud, then review structure, accuracy and safety.
- Session 5 — 45 minutes: complete a timed written practice task based on your current syllabus, then mark it against your notes.
At the end of the week, spend 15 minutes deciding what to revisit. Look for repeat errors: omitted units, incorrect formula use, weak mechanism, or a failure to state the emergency implication. Keep a short error log and make the next week's plan from it. If your available time is limited, retain the retrieval and correction sessions; reduce passive rereading first.
How MySummaries helps
MySummaries lets you make a revision board from your own PDFs, slides and photographed handwritten notes, then use that board for spaced-repetition flashcards, written practice, oral-exam practice and audio lectures. For ACEM Primary preparation, use it to keep core science and its acute-care application together, practise explaining mechanisms, and revisit the specific gaps revealed by your attempts. Open MySummaries.