GAGS and IGA Scoring Systems Are Reliable, Correlated for Acne Severity

A novel study investigated the agreement between observers (inter-observer variation) using the Global Acne Grading System (GAGS) and Investigator Global Assessment of Acne (IGA).

The Global Acne Grading System (GAGS) and Investigator’s Global Assessment (IGA) are reliable for assessing acne severity and are correlated, but quality of life regarding acne is not correlated with the severity of the disease, according to findings from a study published in Clinical, Cosmetic, and Investigational Dermatology.

Researchers sought to investigate the agreement of different observers regarding use of GAGS and IGA, as well as the correlation between the assessment scores and their relationship to the Dermatology Life Quality Index (DLQI) and the Cardiff Acne Disability Index (CADI) quality-of-life scales. The prospective study involved 54 patients (81.5% women) with acne—49 participants (90.7%) were aged 18 to 24 years, and 5 patients (9.3%) were aged 25 to 30 years.

According to the IGA scoring system, most participants (63%) had acne that was mild in severity. The mean score on GAGS was 16.19 ± 5.09, and 42 patients were rated as mild to almost clear by both the IGA and GAGS scoring systems by the 4 evaluators.

The investigators observed a significant association between GAGS and IGA (Pearson chi-square test P = .0001), and the scales demonstrated excellent inter-rater reliability. No correlation was found between IGA and quality of life measures (CADI nor DLQI), although a significant weak correlation was observed between GAGS and CADI.

“This study shows an excellent agreement between investigators of severity using GAGS in terms of intra-rater reliability,” stated the researchers. They acknowledged that neither method took into account the scarring or post-inflammatory pigmentation aspects of the disease and only measured the active lesions (comedones and inflammatory lesions). “To our knowledge, no study has compared these two methods previously,” it was noted.

The study authors noted that many tools are available to assess acne severity, but none is considered universally accepted. “Measuring disease severity is essential for clinical practice in terms of evaluation and follow-ups, and in comparing studies in the literature,” the researchers commented. “Measures are usually subjective ones.”


Alsulaimani H, Kokandi A, Khawandanh S, Hamad R. Severity of acne vulgaris: Comparison of two assessment methods [published online September 28, 2020]. Clin Cosmet Investig Dermatol. doi: