What are the effects of delays in laboratory processing on patient outcomes?

Impact of Laboratory Processing Delays on Patient Outcomes

Laboratory processing delays directly worsen patient outcomes by prolonging emergency department length of stay, delaying critical treatment decisions, and increasing risk of inappropriate anticoagulation in acute coronary syndromes.

Critical Time-Sensitive Clinical Scenarios

Acute Coronary Syndromes

• Delays in aPTT turnaround time result in over- or underanticoagulation for prolonged periods, directly compromising patient safety in STEMI and NSTEMI patients receiving unfractionated heparin 1
• The ACC/AHA explicitly identifies laboratory turnaround delays as a source of variability in care that must be avoided, as measurements should occur 6 hours after dosage changes to maintain therapeutic anticoagulation 1
• Prolonged turnaround times deny patients potentially life-saving therapy and risk exposing others through delayed isolation and contact tracing 1

Bloodstream Infections

• Batching rapid molecular tests (performing once, twice, or three times daily rather than continuously) negates the benefit of rapid turnaround times, delaying the switch from empirical to targeted antimicrobial therapy 1
• Even when rapid identification tests can provide results in approximately 1 hour, delays occur when technical staff are unavailable to perform testing, undermining the true impact of rapid diagnostics 1
• The CDC emphasizes that efficient information flow between laboratorians and clinicians is crucial to minimize treatment delays, with direct correlation between reporting delays and treatment initiation delays 2

Emergency Department Impact

Length of Stay Correlations

• Average ED length of stay correlates significantly with the percentage of laboratory outliers (R² = 0.75; P < 0.01), demonstrating that reducing turnaround time outliers directly reduces patient ED time 3
• Each 1-minute decrease in laboratory TAT associates with 0.50 minutes decrease in ED length of stay across broad patient populations and distinct acuity levels 4
• For a 15-minute TAT reduction, a single ED can potentially admit 386 additional patients annually, representing substantial throughput improvement 4

Specific Delay Patterns

• Median TATs in some institutions reach 170 minutes for hemoglobin and 225 minutes for potassium—drastically longer than the Q-Probes recommended goal of 45 minutes for 90% of tests 5
• The longest intervals contributing to delays are ED waiting time and order processing, not within-laboratory processing time 5
• Laboratory TAT shows positive correlation with patient length of stay, though the fastest 10% of samples can be reported within 35 minutes (hematology) and 65 minutes (biochemistry) 6

Specimen-Specific Considerations

Urine Cultures

• Processing urine specimens beyond 2 hours at room temperature produces colony count changes of ≥1 log₁₀ in approximately 32% of specimens, directly causing misdiagnosis 7
• After overnight storage at room temperature, clinical interpretations change in 8% of specimens with results altered in 16% overall, representing clinically significant diagnostic error 7
• Specimens shift from significant to non-significant growth with an odds ratio of 73.89 (95% CI: 41.28-133.01), indicating high risk of diagnostic error 7
• Refrigeration within 1 hour preserves specimen integrity for up to 24 hours, maintaining 87.3-82.6% agreement with immediate processing for high bacterial counts 7

Fecal Immunochemical Testing

• Processing delays up to 10 days show no strong evidence of affecting FIT performance, though one study identified decreased positivity rates (6% vs 8.7%) with delays of 5 or more days 1
• Programs should establish quality-assurance practices to monitor return times and solicit repeat samples when kits fall outside predetermined acceptability ranges 1
• The proportion of FIT samples that cannot be processed by the laboratory should remain less than 5% as a quality metric 1

Clinical Management During Delays

Risk-Stratified Approach

• Patients with moderate-to-high pre-test probability should initiate empirical treatment immediately as if laboratory confirmation were positive, as delays lead to prolonged infectiousness and inappropriate therapy 2
• Estimate disease likelihood through background prevalence patterns, known exposure history, and clinical severity rather than waiting for laboratory confirmation 2
• For patients with moderate-to-severe clinical features, initiate treatment and obtain imaging regardless of test result availability 2

Systems-Level Solutions

• Implement daily testing protocols rather than batch processing to optimize turnaround time 2
• Aggressively set clinically driven TAT targets and assess performance as the percentage of results achieving this goal, rather than focusing solely on TAT means 3
• Continual evaluation of laboratory service networks through turnaround time performance assessment and quality oversight protocols is essential 2

Common Pitfalls to Avoid

• Never use urine specimens held at room temperature beyond 2 hours without refrigeration, as this produces diagnostic errors in up to 32% of positive cultures 7
• Do not batch rapid molecular tests when continuous processing is feasible, as this negates the clinical benefit of rapid diagnostics 1
• Avoid focusing exclusively on within-laboratory processing time when ED waiting time and order processing contribute more substantially to delays 5
• Do not wait for laboratory confirmation in moderate-to-high pre-test probability patients when empirical treatment is indicated 2