Endpoint reliability is a critical factor in the success of clinical trials, particularly those relying on clinician‑reported outcomes. Estelle Haenel, Chief Medical Officer at Kayentis, shares her perspective on why rater variability remains an often underestimated challenge, how it can affect data interpretability and regulatory confidence, and how expert rater training combined with high‑quality eCOA can significantly strengthen clinical trial evidence.
Estelle Haenel
PharmD PhD,
Chief Medical Officer @Kayentis
Why is rater variability such an important issue in clinical research, particularly in studies using complex ClinRO measures?
Clinician‑reported outcomes are widely used across many research fields and are particularly prevalent in complex and demanding therapeutic areas such as neuroscience. Although these assessments are performed by trained and experienced professionals, they still involve human judgment, interpretation, and behavior. This inherently introduces variability in how rating scales are administered and scored.
The issue is that this variability generates measurement inconsistency unrelated to the treatment under investigation in the study.
When it affects the data, it can compromise the quality and interpretability of trial results. In the worst cases, it can even put endpoint reliability and therefore regulatory evaluations at risk.
Can you describe the types of rater-related variability typically observed in clinical trials?
Rater‑related variability generally falls into two main categories.
The first is inter‑rater variability, which occurs when different evaluators, across multiple sites or countries but also at the same time, administer the same clinical scales differently. This can lead to systematic differences in scores between sites or raters.
The second is intra‑rater variability, which reflects inconsistencies in how the same clinician scores similar patients over time.
What are the downstream consequences of this variability for clinical trials and their outcomes?
Inconsistent assessments weaken endpoint sensitivity and reproducibility. From a statistical perspective, both forms of rater variability introduce statistical noise, and so they make it harder to detect meaningful treatment effects.
From a regulatory standpoint, they raise legitimate concerns about whether observed results truly reflect treatment impact or are simply artifacts of measurement noise.
Ultimately, this can undermine confidence in the entire evidentiary package submitted to regulators, even when the investigational therapy itself is effective.
How can sponsors effectively minimize rater variability in trials relying on complex ClinROs?
Reducing rater variability requires a deliberate, structured approach. First, expert rater training plays a critical role, particularly in therapeutic areas involving complex outcome measures such as neuroscience. High‑quality training programs include rater qualification, standardized training content, calibration exercises which will happen prior to the first ClinRO administration.
Equally important is continuous quality oversight throughout the study. This includes ongoing monitoring of scoring patterns, centralized review of atypical ratings, and clearly defined retraining triggers. Together, these measures help maintain rater performance and consistency over time.
Where does eCOA fit into this strategy?
When expert rater training is combined with a well‑designed electronic Clinical Outcome Assessment solution, the impact on data quality is substantial. eCOA platforms provide structured workflows that guide clinicians through each assessment step, enforce mandatory fields, and avoid transcription errors.
They also ensure time‑stamped, auditable data capture aligned with protocol‑defined procedures. This level of standardization supports consistent assessment practices across sites and significantly reduces avoidable sources of variability.
FDA and EMA have described in many of their guidance issued in recent years the criticality of the ALCOA+ criteria and have confirmed their preference for electronic data collection methods which allow compliance with these criteria.
What is the overall benefit of combining expert rater training with high quality eCOA?
Together, these elements create a closed quality loop. Standardized training harmonizes how assessments are performed, continuous monitoring ensures sustained performance, and the integrated workflow with eCOA systems ensures that only certified clinicians have access and can complete specific assessments, while preventing unqualified or out-of-date raters from administering these scales.
The result is greater reliability, sensitivity, and reproducibility of clinical trial endpoints, strengthening the confidence that observed effects reflect true treatment impact rather than measurement inconsistency.
This is ultimately what regulators, sponsors, and patients are all relying on.
Joined Kayentis as Chief Medical Officer in 2019. Estelle drives the scientific strategy of the company, collaborating with the scientific advisory board and focusing on patient and site engagement. She has 25+ years of experience in pre-clinical and clinical research in Top 5 Pharma and Biotech companies. A Doctor of Pharmacy, Estelle also has a Masters in Endocrinology and Cellular Interaction and a PhD in Biochemistry and Molecular Biology.
