In an adult presenting with chest pain suggestive of acute coronary syndrome, how does a point‑of‑care troponin test compare to a serum high‑sensitivity troponin assay for diagnosing acute myocardial injury?

Point-of-Care vs. Serum High-Sensitivity Troponin for Acute Myocardial Injury

Central laboratory high-sensitivity troponin assays are strongly preferred over point-of-care troponin tests because POC assays have substantially lower sensitivity, lower diagnostic accuracy, and lower negative predictive value, which compromises their ability to safely rule out acute myocardial infarction. 1

Why Central Laboratory hs-cTn Is Superior

Analytical Performance Differences

• High-sensitivity troponin assays in central laboratories detect troponin in 50-95% of healthy individuals, whereas most point-of-care tests fail to meet high-sensitivity criteria and detect troponin in fewer than 50% of healthy people 1, 2

• Central laboratory hs-cTn assays achieve limits of detection of 1-5 ng/L with a coefficient of variation <10% at the 99th percentile, representing a 10-50 fold improvement over conventional assays 2

• Point-of-care tests cannot reliably measure troponin concentrations in the critical low range (below 20 ng/L) where early myocardial injury must be detected or excluded 1, 2

Clinical Impact on Diagnosis

• The shorter turnaround time advantage of POC tests is completely counterbalanced by their inferior sensitivity, which leads to missed diagnoses of acute MI, particularly in patients presenting early after symptom onset 1

• Central laboratory hs-cTn enables validated 0h/1h and 0h/2h rapid rule-out algorithms that safely discharge 60-78% of low-risk patients with negative predictive values approaching 100%, whereas POC assays have not been validated for these accelerated protocols 2, 3

• Automated central laboratory assays have been more thoroughly evaluated in large multicenter studies and consistently demonstrate higher diagnostic accuracy for MI at presentation compared to POC tests 1

Guideline Recommendations

• The 2020 ESC Guidelines explicitly state that the majority of currently used point-of-care tests cannot be considered sensitive or high-sensitivity assays, and therefore automated central laboratory assays are preferable 1

• The 2014 AHA/ACC Guidelines note that point-of-care troponin values may provide initial diagnostic information, but their sensitivity is substantially below that of central laboratory methods, and rigorous quantitative assay standardization needed for routine diagnosis favors central laboratory testing 1

• No current guideline recommends POC troponin as equivalent to central laboratory hs-cTn for definitive diagnosis or serial monitoring 1, 3

When POC Troponin Might Be Considered

Limited Acceptable Use Cases

• POC troponin may provide preliminary information in resource-limited settings where central laboratory access is delayed beyond 60-90 minutes, but any positive or borderline POC result must be confirmed with central laboratory hs-cTn before making treatment decisions 1

• In one small 2022 study (n=136), a newer qualitative POC-cTnI assay showed 91.76% sensitivity and 98.04% specificity when combined with 0h and 3h measurements, but this single-center study cannot override the consistent evidence from large multicenter trials favoring central laboratory testing 4

Critical Pitfalls of POC Testing

• POC assays miss 8-15% of patients with true myocardial injury who have low but elevated hs-cTn concentrations detectable only by central laboratory methods 2, 3

• POC tests lack the precision to detect the small absolute changes (e.g., 4-7 ng/L over 1-2 hours) that are diagnostic of acute MI in validated rapid protocols 2, 3

• Using POC troponin for serial monitoring creates false reassurance because the assay cannot reliably distinguish a 20% relative change or clinically significant absolute delta at low concentrations 1, 2

Practical Implementation Algorithm

For Emergency Department Evaluation

1. Order central laboratory hs-cTn at presentation (0 hour) for all patients with chest pain or suspected acute coronary syndrome 1, 3

2. Obtain 12-lead ECG within 10 minutes; if STEMI is present, activate catheterization laboratory immediately without waiting for troponin results 3

3. If initial hs-cTn is below assay-specific rule-out threshold (e.g., <5 ng/L for hs-cTnI or <6 ng/L for hs-cTnT) and symptom onset was >3 hours prior, patient can be ruled out with a single measurement 3

4. If initial hs-cTn is in the intermediate zone or symptom onset was <3 hours, repeat hs-cTn at 1 hour (preferred) or 2 hours (second-line) using the same central laboratory assay 3

5. Rule-in acute MI if baseline hs-cTnI >40 ng/L or if absolute change >4 ng/L over 1 hour (for validated assays) with at least one value above the 99th percentile 3

6. Never use POC troponin for serial measurements in validated rapid protocols; these algorithms were developed and validated exclusively with central laboratory hs-cTn assays 2, 3

Interpretation of Discordant Results

• If a POC troponin is negative but clinical suspicion remains high (ongoing chest pain, dynamic ECG changes, hemodynamic instability), immediately order central laboratory hs-cTn and do not rely on the POC result to exclude MI 1

• Elevated hs-cTn in the absence of ischemic symptoms or ECG changes requires evaluation for non-ACS causes including heart failure, myocarditis, pulmonary embolism, sepsis, chronic kidney disease, and tachyarrhythmias 1, 3

• In elderly patients with renal dysfunction (eGFR <30 mL/min/1.73 m²), do not attribute elevated hs-cTn to impaired clearance alone; underlying cardiac disease is the primary driver and warrants investigation 1, 3

Turnaround Time Considerations

• Central laboratory hs-cTn results are typically available within 60 minutes, which is clinically acceptable and does not justify the diagnostic compromise of using POC assays 3

• If institutional turnaround time exceeds 90 minutes, address laboratory workflow inefficiencies rather than substituting inferior POC testing 1