Analyze and predict recruitment efficiency for clinical trial protocols.
Recruitment Results
Screen Failure Rate:0%
Total Screen Failures:0 participants
Screening Ratio:0:1 (Screened to Randomized)
Understanding Screen Failure Rates in Clinical Trials
In clinical research, a screen failure occurs when a potential participant signs an informed consent form (ICF) and undergoes screening procedures but is ultimately found ineligible for randomization into the study. This usually happens because they fail to meet one or more inclusion or exclusion criteria defined in the study protocol.
The Screen Failure Rate (SFR) is a critical KPI for clinical operations teams, project managers, and CRAs. It directly impacts study timelines, site selection, and the overall clinical trial budget.
The Screen Failure Formula
The calculation is straightforward but essential for site feasibility:
Screen Failure Rate (%) = [(Total Screened – Total Randomized) / Total Screened] × 100
Why Monitoring This Metric is Vital
Budget Planning: Screening procedures (labs, imaging, exams) cost money. A high failure rate means higher costs per randomized subject.
Timeline Projections: If you need 100 patients and your failure rate is 50%, you must find and screen 200 patients.
Protocol Feasibility: Excessively high failure rates often indicate that the inclusion/exclusion criteria are too restrictive, potentially requiring a protocol amendment.
Site Performance: Sites with high failure rates may be struggling to pre-screen effectively or may be located in areas with a mismatching patient demographic.
Practical Example
Metric
Scenario A (Oncology)
Scenario B (Vaccine)
Target Randomization
50
500
Historical SF Rate
70%
15%
Required Screenings
167
588
Common Causes of High Screen Failure Rates
Strict Laboratory Values: Narrow windows for hemoglobin, creatinine, or liver enzymes.
Comorbidities: Excluding patients with common secondary conditions (e.g., controlled hypertension).
Washout Periods: Patients unable or unwilling to stop current medications for the required duration.
Diagnostic Verification: Failure to confirm the specific sub-type or genetic marker of a disease through central reading.
function calculateSF() {
var totalS = document.getElementById("totalScreened").value;
var totalR = document.getElementById("totalRandomized").value;
var nS = parseFloat(totalS);
var nR = parseFloat(totalR);
// Validation
if (isNaN(nS) || isNaN(nR)) {
alert("Please enter valid numerical values.");
return;
}
if (nS nS) {
alert("Total Randomized cannot exceed Total Screened. Please check your data.");
return;
}
// Calculations
var failures = nS – nR;
var rate = (failures / nS) * 100;
var ratio = (nS / nR).toFixed(2);
// Display
document.getElementById("resRate").innerHTML = rate.toFixed(2);
document.getElementById("resFailures").innerHTML = failures.toLocaleString();
document.getElementById("resRatio").innerHTML = isFinite(ratio) ? ratio : "N/A";
document.getElementById("sfResultBox").style.display = "block";
// Scroll to result
document.getElementById("sfResultBox").scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}