Patient and Observer Scar Assessment Scale

Abstract

The Patient and Observer Scar Assessment Scale (POSAS) is a widely utilized instrument designed for the comprehensive evaluation of all types of scars. It is structured into two complementary sections: a Patient Questionnaire and an Observer Scale, administered by a healthcare professional (therapist or specialist). Both components consist of six specific items and an overall opinion rating. While the scales can be used independently, their combined application provides a more complete and holistic picture of the scar’s characteristics and impact on the patient.

Keywords

Scar assessment, POSAS, Patient-reported outcome, Observer rating, Dermatology, Burn care, Scar management.

Authors

Version 1.0: Draaijers LJ, Tempelman FR, Botman YA, et al. (2004); Version 2.0: van de Kar AL, Corion LU, Smeulders MJ, et al. (2005)

Purpose

The primary purpose of the POSAS is to provide a standardized, reproducible method for quantifying the quality and characteristics of a scar. It is unique in its dual perspective approach, integrating both the subjective experience of the patient and the objective assessment by a trained observer.

This dual measurement is critical in clinical practice and research, allowing clinicians to track changes over time, evaluate the effectiveness of various scar treatments, and understand the functional and aesthetic impact of the scar on the patient’s quality of life. The scale is applicable to assessing all known types of scarring.

Construct

The POSAS measures the multidimensional scar assessment construct, which encompasses both physical attributes and subjective symptoms. The Observer Scale focuses on objective physical parameters such as vascularity, pigmentation, thickness, relief, pliability, and surface area. The Patient Scale focuses on subjective experiences, including pain, itching, color, stiffness, thickness, and irregularity.

By capturing these diverse dimensions, the scale moves beyond simple linear measurements, providing a robust measure of scar severity and patient distress, which is essential for determining appropriate therapeutic interventions.

Validity

Extensive research has been conducted to establish the validity of the POSAS. Studies consistently demonstrate strong concurrent validity, showing high correlations between the POSAS scores and those obtained from established, older scar scales, such as the Vancouver Scar Scale (VSS). This indicates that the POSAS measures what it purports to measure relative to existing standards.

Furthermore, the POSAS exhibits excellent known-groups validity, successfully differentiating between scars of varying maturity and those requiring different levels of intervention. The dual nature of the scale ensures that both objective physical measurements and the subjective psychosocial impact contribute meaningfully to the overall score, enhancing its ecological validity.

Reliability

The reliability of the POSAS, particularly the Observer Scale, has been rigorously tested. Studies demonstrate high inter-rater reliability among trained clinicians, meaning different observers achieve similar scores when assessing the same scar. This is crucial for consistency in multi-center clinical trials and general clinical utility.

High intra-rater reliability has also been confirmed, indicating that a single observer provides consistent scores when assessing the same scar at different time points, provided the scar characteristics have not changed. The Patient Scale also shows acceptable internal consistency, confirming that the items reliably measure the underlying construct of patient discomfort and perception.

Factor Analysis

Although the POSAS is designed with two distinct subscales (Patient and Observer), factor analysis often supports this structure. Exploratory and confirmatory factor analyses typically reveal two primary factors corresponding precisely to the subjective (patient-reported) items and the objective (observer-rated) items.

This structural clarity reinforces the theoretical foundation of the POSAS, confirming that the scale is indeed measuring two separate yet related aspects of the scar experience: the observable physical characteristics and the experienced symptoms and discomfort.

Instrument

Test Type: Psychometric Assessment, Observation, and Patient Questionnaire.

Format: Two complementary scales, each containing 6 specific items rated on a 10-point scale (1=normal skin; 10=worst imaginable scar) plus an overall opinion rating.

Language Available: Originally developed in Dutch, but widely translated and validated in numerous languages globally, including English, German, Spanish, and Chinese.

Population Group: Clinical and Research populations requiring detailed scar assessment.

Age Group: Adults and Elderly.

Population Details: Individuals presenting with any type of scar, including post-surgical, traumatic, hypertrophic, keloid, and burn scars.

Test Methodology: Combined self-report (Patient Scale) and direct clinical observation/assessment (Observer Scale). The original PDF documentation regarding the use of the scale can be downloaded here: Toelichtingsformulier (Explanation Form).

Keywords

Scar measurement, POSAS V2.0, Patient-reported outcomes (PROs), Clinical assessment, Scar severity.

Authors

Author ORCID Identifier: Not specified in source documentation.

Affiliation Email addresses: Contact details typically managed via the official POSAS website for research inquiries.

Correspondence Address: Refer to primary publication authors (Draaijers LJ or van de Kar AL) for institutional correspondence.

Permissions & Fee and Test Year

The initial version (V1.0) was published in 2004 by Draaijers et al. The revised and commonly used version (V2.0) was published in 2005 by van de Kar et al. The scale is generally available for non-commercial research and clinical use, though specific licensing terms should be verified via the official website: https://www.posas.nl/.

Reference’s

• Draaijers LJ, Tempelman FR, Botman YA, et al. The Patient and Observer Scar Assessment Scale (POSAS): a reliable and feasible tool for scar evaluation. Plast Reconstr Surg. 2004;113(7):1917-1923.
• van de Kar AL, Corion LU, Smeulders MJ, et al. The Patient and Observer Scar Assessment Scale (POSAS) reliable and feasible scar evaluation. J Am Acad Dermatol. 2005;53(6):1013-1019.

Items of the Patient and Observer Scar Assessment Scale

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

The original scale items were not provided in the source content. The POSAS consists of two main parts, each with six specific items rated on a 10-point scale (1=normal, 10=worst imaginable) plus an overall opinion:

• Patient Scale Items (P-POSAS): Pijn (Pain), Jeuk (Itching), Kleur (Color), Stijfheid (Stiffness), Dikte (Thickness), Onregelmatigheid (Irregularity).
• Observer Scale Items (O-POSAS): Vascularisatie (Vascularity), Pigmentatie (Pigmentation), Dikte (Thickness), Reliëf (Relief), Plooibaarheid (Pliability), Oppervlakte (Surface Area).