5.5 Physical Assessment and Point-of-Care Testing
Key Takeaways
- Point-of-care testing supports but does not replace clinical assessment, and every device requires quality control, operator training, and a documented result.
- A capillary point-of-care international normalized ratio is not interchangeable with a laboratory venous value and becomes less reliable at high values and in antiphospholipid syndrome.
- Orthostatic hypotension is defined as a fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing.
- Point-of-care glycated hemoglobin devices vary in accuracy and are unreliable in hemoglobinopathies, recent transfusion, pregnancy, and conditions altering red cell turnover.
- Pulse oximetry measures oxygen saturation rather than ventilation, and it is falsely normal or high in carbon monoxide poisoning.
5.5 Physical Assessment and Point-of-Care Testing
Exam Focus: The blueprint pairs "clinical biochemistry and diagnostic testing (including point-of-care testing)" in a single subcategory, and the syllabus separately requires "completion of a comprehensive patient assessment (including relevant physical assessments)". Items usually turn on a technique error or a device limitation.
Vital Signs and Their Drug Therapy Meaning
| Sign | Normal adult range | Common drug-related interpretation |
|---|---|---|
| Blood pressure | Under 120/80 mmHg optimal | Efficacy of antihypertensives; orthostatic drop from alpha-blockers, diuretics, nitrates |
| Heart rate | 60 to 100 beats per minute | Bradycardia from beta-blockers, non-dihydropyridine calcium channel blockers, digoxin; tachycardia from salbutamol, decongestants, withdrawal |
| Respiratory rate | 12 to 20 breaths per minute | Depression with opioids and sedatives; elevation in metabolic acidosis |
| Temperature | About 36.5 to 37.5 degrees Celsius | Infection; drug fever; neuroleptic malignant syndrome; serotonin syndrome |
| Oxygen saturation | 95 to 100 percent on room air | Target 88 to 92 percent in those at risk of carbon dioxide retention |
Orthostatic vital signs are measured supine after five minutes, then standing at one and three minutes. A fall of 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing, or a rise in heart rate above about 20 beats per minute, defines orthostatic hypotension. In an older adult presenting with falls or dizziness, this single measurement frequently identifies the responsible drug.
Pain is assessed as a vital sign using a numeric or visual analogue scale, with attention to onset, provocation, quality, radiation, severity, and timing.
Focused Physical Assessment Within Pharmacist Scope
Pharmacists in Canada perform focused assessment relevant to medication decisions rather than diagnostic examination.
- Weight, height, and body mass index, plus waist circumference, are needed for dosing, for renal function estimation, and for cardiometabolic risk.
- Peripheral edema is graded by pitting depth and recovery time and points to calcium channel blockers, thiazolidinediones, gabapentinoids, or worsening heart failure.
- Injection and infusion sites are inspected for lipohypertrophy, erythema, and induration.
- Skin assessment covers rash morphology and distribution, and the identification of severe cutaneous reactions.
- Inhaler and device technique observation is a physical assessment in its own right and is more informative than any patient self-report.
- Cognitive and functional screening where a validated tool is used, alongside falls risk assessment.
Refer promptly rather than continuing to assess where there is chest pain, focal neurological deficit, respiratory distress, signs of sepsis, or a rapidly evolving rash with mucosal involvement.
Point-of-Care Testing: Principles
Point-of-care testing is diagnostic testing performed near the patient with a rapid result. In pharmacy it supports screening, monitoring, and treatment decisions, and provincial authority for specific tests varies.
Every point-of-care program requires:
- Training and demonstrated competence for every operator.
- Quality control at the intervals the manufacturer specifies and after every new reagent lot, with documented results and defined action when control values fall outside range.
- Documentation of the result in the patient record, with the device and lot identified.
- A defined action pathway — what result triggers what response, including referral.
- Infection control and sharps management, since almost all involve capillary blood.
- Informed consent, explaining what the test does and does not establish.
The unifying limitation is that a point-of-care result is not interchangeable with a laboratory result. Devices use different methods and calibrations, and a decision at a clinical threshold should be confirmed by laboratory testing.
Common Tests and Their Traps
| Test | Use | Key limitations |
|---|---|---|
| Capillary blood glucose | Diabetes monitoring, hypoglycemia | Falsely high with sugar residue on the skin; affected by hematocrit, temperature, and altitude |
| Glycated hemoglobin (A1C) | Glycemic control over roughly 3 months | Unreliable in hemoglobinopathies, recent transfusion, hemolysis, iron deficiency, pregnancy, and advanced kidney disease; device accuracy varies |
| Lipid panel | Cardiovascular risk screening | Non-fasting acceptable for most screening; triglycerides are most affected by recent food |
| International normalized ratio (INR) | Warfarin monitoring | Capillary and venous values are not interchangeable; less reliable at high INR and unreliable in antiphospholipid syndrome |
| Rapid strep antigen | Pharyngitis triage | Good specificity but imperfect sensitivity; a negative in a high-probability child may need culture |
| Influenza and COVID-19 antigen | Respiratory triage | Sensitivity depends on timing, symptom stage, and swab technique; a negative result does not exclude infection |
| Pulse oximetry | Oxygenation | Measures saturation, not ventilation or carbon dioxide; unreliable with poor perfusion, nail polish, and motion; falsely reassuring in carbon monoxide poisoning; accuracy can be reduced at higher skin pigmentation |
| Spirometry | Airflow obstruction | Highly effort-dependent; requires trained coaching and acceptable, repeatable manoeuvres |
Carbon monoxide poisoning deserves emphasis. Carboxyhemoglobin absorbs light similarly to oxyhemoglobin at the wavelengths a standard pulse oximeter uses, so the displayed saturation can be normal while the patient is severely hypoxic. Diagnosis requires co-oximetry, and the treatment is high-flow oxygen.
Interpreting Any Test Result
Four questions apply to every point-of-care and laboratory result:
- Is the result plausible given the patient in front of you? A result that contradicts the clinical picture is repeated, not acted on.
- Was the pre-analytical process correct? Technique, sample quality, timing relative to doses, and device maintenance produce more errors than the analytic step.
- What is the pre-test probability? In a low-prevalence population, even a specific test produces a substantial proportion of false positives, which is why screening asymptomatic people rarely helps.
- What action will follow? A test that will not change management should not be performed.
Communicate results in plain language, explain what a negative result does and does not exclude, document the result and the action taken, and share it with the patient's other providers where it affects their care.
A patient is found unconscious in a garage with a running engine. The pulse oximeter reads 99%. How should this be interpreted?
An 81-year-old on tamsulosin, furosemide, and amlodipine reports dizziness on standing. Supine blood pressure is 138/78 mmHg; after two minutes standing it is 112/70 mmHg. How is this interpreted?
Which situation makes a point-of-care glycated hemoglobin result unreliable?
Before offering point-of-care international normalized ratio testing in a community pharmacy, which element is essential?