How to Calculate Screen Failure Rate in Clinical Trials

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How to Calculate Screen Failure Rate in Clinical Trials

Screen failure rate (SFR) is a critical Key Performance Indicator (KPI) in clinical operations. It measures the efficiency of the recruitment process by identifying the percentage of potential participants who underwent screening but did not meet the eligibility criteria for randomization.

High screen failure rates can significantly inflate trial budgets, extend timelines, and increase the workload for site staff without contributing to the study's data endpoints.

The Screen Failure Rate Formula

To calculate the screen failure rate, you need two primary data points: the total number of subjects screened and the total number of subjects successfully enrolled (randomized). The formula is derived as follows:

Screen Failures = Total Screened – Total Enrolled

Screen Failure Rate (%) = (Screen Failures / Total Screened) × 100

Example Calculation

Consider a Phase II oncology study with the following metrics:

• Total Screened: 200 patients signed informed consent.
• Total Enrolled: 50 patients were randomized into treatment arms.

First, calculate the absolute number of failures: 200 – 50 = 150 failures.
Then, apply the percentage formula: (150 / 200) × 100 = 75% Screen Failure Rate.

Financial Impact of High SFR

Screen failures are often categorized as "sunk costs." While some screening procedures are standard of care, trial-specific screening (e.g., genomic testing, specific imaging) is billed to the sponsor. If a screening visit costs $2,000 and you have 150 failures, that is $300,000 in direct costs that yielded no randomization data.

Common Causes of Screen Failures

• Inclusion/Exclusion Criteria: Criteria that are too restrictive or poorly defined.
• Patient Burden: Invasive screening procedures leading to patient withdrawal before randomization.
• Protocol Complexity: Narrow therapeutic windows or complex wash-out periods.
• Operational Issues: Scheduling delays causing lab values to expire.

Improving Enrollment Efficiency

To reduce the screen failure rate, sponsors often implement pre-screening questionnaires to filter out ineligible candidates before they sign the Informed Consent Form (ICF). Additionally, reviewing the protocol for non-essential exclusion criteria can broaden the eligible population and improve the Enrollment Rate (Enrollment Efficiency).

function calculateScreenFailure() { // Get input elements var screenedInput = document.getElementById('totalScreened'); var enrolledInput = document.getElementById('totalEnrolled'); var costInput = document.getElementById('costPerScreen'); var resultBox = document.getElementById('sfr-results'); var screenedError = document.getElementById('screenedError'); var enrolledError = document.getElementById('enrolledError'); // Reset errors and results screenedError.style.display = 'none'; enrolledError.style.display = 'none'; resultBox.style.display = 'none'; // Parse values var totalScreened = parseFloat(screenedInput.value); var totalEnrolled = parseFloat(enrolledInput.value); var costPerVisit = parseFloat(costInput.value) || 0; // Validation Logic var isValid = true; if (isNaN(totalScreened) || totalScreened <= 0) { screenedError.style.display = 'block'; isValid = false; } if (isNaN(totalEnrolled) || totalEnrolled totalScreened) { enrolledError.style.display = 'block'; enrolledError.innerText = "Enrolled subjects (" + totalEnrolled + ") cannot exceed Screened subjects (" + totalScreened + ")."; isValid = false; } if (!isValid) return; // Calculations var numFailures = totalScreened – totalEnrolled; var failureRate = 0; var enrollmentRate = 0; if (totalScreened > 0) { failureRate = (numFailures / totalScreened) * 100; enrollmentRate = (totalEnrolled / totalScreened) * 100; } var totalWastedCost = numFailures * costPerVisit; // formatting numbers var failureRateFormatted = failureRate.toFixed(2) + "%"; var enrollmentRateFormatted = enrollmentRate.toFixed(2) + "%"; var costFormatted = "$" + totalWastedCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); // Color coding based on rate (Standard industry thresholds: >50% is often considered high depending on phase/indication) var rateColor = failureRate > 50 ? "#dc3545" : "#28a745″; // Red if high, Green if low (simplified logic) // Generate HTML Output var outputHTML = "; outputHTML += ''; outputHTML += ''; outputHTML += ''; if (costPerVisit > 0) { outputHTML += ''; } // Display results resultBox.innerHTML = outputHTML; resultBox.style.display = 'block'; }