Professional Detailing2 min read

Missing Follow-Up Visits in Coating Trials: Do Not Count Unknown Results as Passes

Report missing coating-trial follow-ups as unknown outcomes and keep enrolled, inspected and passing sample counts visible.

Updated · NANOLAB Knowledge

A coating trial can look more successful when only customers who return are included. Missing follow-up observations are unknown outcomes, not automatic passes or failures. Reporting them clearly protects the usefulness of the study.

Show the full observation flow

Suppose an illustrative trial enrolls 20 vehicles. Twelve return for the planned inspection and ten meet the defined criterion. The observed pass share among inspected vehicles is 10 of 12, or about 83 percent. Across all enrolled vehicles, ten confirmed passes are known; eight outcomes remain unobserved.

It would be misleading to say that 83 percent of all 20 vehicles passed without addressing the missing observations. It would also be incorrect to label all eight missing vehicles failures by default.

Record why observations are missing

Separate scheduling problems, sold vehicles, withdrawn participation and inability to inspect. Some reasons may be related to the outcome. Customers with especially good or especially poor experiences may be more likely to respond, making the observed group unrepresentative.

Keep the follow-up window consistent. An inspection at one month is not a substitute for a planned six-month observation unless it is explicitly reported as a different time point.

Use cautious summaries

Report enrolled, eligible, inspected and missing counts alongside the observed results. For an internal decision, examine how plausible outcomes among the missing cases could change the conclusion. Formal handling of missing data may require statistical advice.

Use this information to improve follow-up procedures, not to pressure customers into a preferred result. A transparent small trial with clearly reported gaps is more informative than a polished success percentage whose denominator quietly excludes inconvenient or unavailable cases. Keep any published claim within what was actually observed.

Related guidance

For product-specific application instructions, consult NANOLAB technical documentation or ask about your surface and intended use.