An abnormal result can represent an emergency, a developing trend, a condition needing prompt investigation or a measurement that requires verification.
The number does not make that decision alone. Symptoms, previous results, medicines, sample quality and the patient's circumstances all affect what should happen next.
This quiz contains six fictional adult cases. The reference intervals are illustrative and may differ from those used by a particular laboratory. They are included to make the exercises interpretable, not to establish universal ranges.
For each panel, identify the priority action and explain why a less urgent or more automatic response would be inappropriate.
Panel 1: the comparison changes the result
A 70-year-old has had diarrhoea and poor oral intake for two days. They report reduced urine output and light-headedness on standing. Their creatinine was 90 micromol/L two days ago.
| Test | Current result | Illustrative reference interval |
|---|---|---|
| Sodium | 138 mmol/L | 135-145 mmol/L |
| Potassium | 4.8 mmol/L | 3.5-5.3 mmol/L |
| Urea | 14.0 mmol/L | 2.5-7.8 mmol/L |
| Creatinine | 160 micromol/L | 60-110 micromol/L |
Choose the next step: routine review in three months, or prompt same-day clinical assessment for an acute kidney injury and its cause?
Explain: which information makes this more than an isolated mildly elevated creatinine?
Panel 2: the ECG does not close the question
A patient with chronic kidney disease has a laboratory-confirmed potassium result from a sample reported as non-haemolysed. They are being assessed clinically. The initial ECG does not show an obvious hyperkalaemic change.
| Test | Result | Illustrative reference interval |
|---|---|---|
| Potassium | 6.7 mmol/L | 3.5-5.3 mmol/L |
| Sodium | 139 mmol/L | 135-145 mmol/L |
| Creatinine | 210 micromol/L | 60-110 micromol/L |
| Bicarbonate | 19 mmol/L | 22-29 mmol/L |
Choose the next step: urgent monitored hospital management, or reassurance with a routine repeat next week because the ECG appears normal?
Explain: what does the ECG establish, and what does it fail to establish?
Panel 3: neurological symptoms with a low sodium
A 68-year-old recently started a thiazide-type diuretic. They have become confused and have now had a seizure. The following results are available during the emergency assessment.
| Test | Result | Illustrative reference interval |
|---|---|---|
| Sodium | 118 mmol/L | 135-145 mmol/L |
| Potassium | 3.8 mmol/L | 3.5-5.3 mmol/L |
| Measured plasma osmolality | 250 mOsm/kg | 275-295 mOsm/kg |
| Glucose | 5.3 mmol/L | 4.0-7.8 mmol/L, non-fasting |
Choose the next step: emergency monitored assessment and treatment, or outpatient investigation of the likely medication cause before responding to the neurological symptoms?
Explain: why is identifying a possible cause not the same as completing the immediate management?
Panel 4: calcium and a changing mental state
A 73-year-old presents with increasing thirst, constipation, drowsiness and clinical dehydration. There is no established explanation for the result.
| Test | Result | Illustrative reference interval |
|---|---|---|
| Albumin-adjusted calcium | 3.60 mmol/L | 2.20-2.60 mmol/L |
| Albumin | 40 g/L | 35-50 g/L |
| Creatinine | 145 micromol/L | 60-110 micromol/L |
| Sodium | 142 mmol/L | 135-145 mmol/L |
Choose the next step: urgent hospital treatment and investigation, or a routine repeat calcium in several weeks while waiting for a PTH result?
Explain: which features make the timing important?
Panel 5: a replacement prescription is not the whole plan
A 65-year-old man has several months of fatigue. He is currently haemodynamically stable, without chest pain, acute breathlessness or visible ongoing bleeding. The reason for the abnormal results is not known.
| Test | Result | Illustrative reference interval |
|---|---|---|
| Haemoglobin | 94 g/L | 130-180 g/L |
| MCV | 70 fL | 80-100 fL |
| Ferritin | 7 micrograms/L | 30-400 micrograms/L |
| White cell count | 6.2 x 10^9/L | 4.0-11.0 x 10^9/L |
| Platelets | 350 x 10^9/L | 150-400 x 10^9/L |
Choose the next step: investigate the cause and plan appropriate replacement and follow-up, or assume poor dietary intake and prescribe indefinitely without further assessment?
Explain: what question remains after recognising iron deficiency?
Panel 6: a low count with a sample warning
A clinically well adult has an unexpected low platelet count. There is no current bleeding, and the analyser report flags possible platelet clumping.
| Test | Result | Illustrative reference interval |
|---|---|---|
| Haemoglobin | 132 g/L | 120-160 g/L |
| White cell count | 6.4 x 10^9/L | 4.0-11.0 x 10^9/L |
| Platelets | 45 x 10^9/L | 150-400 x 10^9/L |
| Laboratory comment | Possible platelet clumps | Not applicable |
Choose the next step: promptly discuss the result with the laboratory and arrange film review and reliable repeat measurement, or diagnose immune thrombocytopenia and begin treatment from this number alone?
Explain: why would simply ignoring the result also be inadequate?
Answers and explanations
1. Assess the acute change promptly
The rise from 90 to 160 micromol/L over two days, together with reduced urine output and an acute illness, changes the interpretation.
The NHS Greater Glasgow and Clyde AKI guidance emphasises assessment of fluid balance, sepsis, obstruction, urinalysis and medicines.
Volume depletion is plausible, but it should not become the only explanation considered. Assess the patient, review the medicine list and decide the appropriate location and intensity of care.
A fluid plan must fit the clinical assessment, including the risk of overload. “Creatinine is raised” is not itself a complete fluid prescription.
The stat game includes separate next-step decisions in which a changing result can matter more than an isolated value.
2. Treat severe hyperkalaemia as urgent despite an initially reassuring ECG
The UK Kidney Association hyperkalaemia guideline recommends urgent hospital assessment for severe hyperkalaemia at or above 6.5 mmol/L and appropriate cardiac monitoring.
The absence of an obvious ECG change is not a basis for a routine wait. Progress urgent reassessment and treatment through the relevant monitored pathway, including verification where needed without introducing unsafe delay.
The question specifies a non-haemolysed sample to avoid making sample artefact the intended answer. It does not eliminate the need to understand how the result was obtained.
Do not equate one ECG with a guarantee that the potassium level cannot cause harm.
3. Respond to the symptomatic hyponatraemia now
The patient has profound hyponatraemia with serious neurological symptoms.
The GGC hyponatraemia guidance identifies severe symptoms as requiring urgent treatment because of the neurological consequences.
Emergency assessment, seizure management and a specialist-guided monitored correction plan take priority over an outpatient search for the cause.
The new medicine is relevant but does not establish the entire mechanism. Other contributors and the duration of the sodium disturbance still require assessment.
This article intentionally does not provide a stand-alone correction regimen. The objective is to select the appropriate setting and urgency, not to normalise a dangerous value using an improvised fluid instruction.
4. Treat the severe hypercalcaemia urgently
An adjusted calcium above 3.5 mmol/L, especially with drowsiness, dehydration and renal impairment, requires urgent treatment.
The GGC hypercalcaemia guideline describes the urgency and the need to tailor rehydration to the patient's clinical state, with caution where fluid overload is a concern.
Investigation of the cause should proceed, including appropriate PTH testing and clinical assessment. Waiting for the explanatory result should not postpone responding to the current physiological problem.
The result does not, by itself, diagnose malignancy or primary hyperparathyroidism. Treatment of the immediate disturbance and identification of its cause are related but separate tasks.
5. Establish why the patient is iron deficient
The low haemoglobin, microcytosis and low ferritin support iron-deficiency anaemia in this constructed case.
The remaining question is why it has developed. The NHS iron-deficiency guidance describes further investigation when the cause is unclear, including assessment for gastrointestinal blood loss and referral where appropriate.
Plan suitable replacement and monitoring while progressing the investigation. Do not assume that a dietary explanation is sufficient without assessing the history and relevant causes.
The scenario is deliberately stable and chronic. New active bleeding, chest pain, syncope or deterioration would alter the urgency and immediate management.
6. Verify the count without dismissing it
Possible platelet clumping raises concern that the automated count may not reflect the true circulating platelet number.
The Haematologica review of spuriously low platelet counts emphasises blood-film examination and accurate measurement. It also explains that changing the sample anticoagulant does not prevent clumping in every case.
Discuss the result promptly with the laboratory. The appropriate repeat method may include an alternative sample or processing approach according to laboratory advice.
Do not jump directly from this result to immune thrombocytopenia treatment. Equally, possible artefact does not prove the true count is normal or exclude coexisting genuine thrombocytopenia.
A practical order for reviewing results
First, establish whether the patient is unwell now. Next, inspect the result's severity, trend and reliability. Then identify the clinical question that needs answering and who will act on it.
This order is an editorial review aid, not a validated scoring instrument.
A result can be numerically striking but technically unreliable. Another can look modestly abnormal while representing a major change from baseline. A third can be correct and important without demanding the same response as a symptomatic emergency.
The action should follow the combination.
Do not let the result become an unowned task
In teaching, ask who would contact the patient, which team would receive the escalation and what would happen if the patient could not be reached.
Those operational questions do not replace medical interpretation. They ensure that the interpretation becomes an actual plan.
A note saying "repeat bloods" is incomplete when no timeframe, responsible person or response to deterioration has been established.
For a fresh decision exercise, stat supplies three separate UK-context scenes. Today's edition is not guaranteed to concern laboratory medicine.
Frequently asked questions
Are the reference intervals universal?
No. The intervals are illustrative adult ranges for the fictional exercises. Actual reports must be interpreted using the laboratory method, units and relevant patient context.
Should every abnormal result be repeated before treatment?
No. Verification can be important, but urgent assessment and treatment should not be delayed when the clinical situation already requires them.
Does a normal ECG make severe hyperkalaemia safe to review routinely?
No. The potassium level and clinical context still require urgent assessment and appropriate monitoring. The ECG is one part of the evaluation.