Hidradenitis Suppurativa Severity Tool Addresses Limitations of Current Measures


Recent data showed that a new HS-IGA tool for hidradenitis suppurativa addressed several concerns of prior tools but also maintained certain limitations.

Amit Garg, MD

Credit: feinstein.northwell.edu

Amit Garg, MD

Credit: feinstein.northwell.edu

The Hidradenitis Suppurativa Investigator Global Assessment (HS-IGA) shows strong psychometric properties when compared to current HS measurements, according to new findings.1

The general lack of simplified measures of severity and response in trials may lead to less drug development and there may be a need for clinical settings to have feasible instruments. As a result, this analysis was authored by Amit Garg, MD, from the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell in New York.

A substantial proportion of those with HS feel pessimistic about effectively managing their symptoms, with almost half of patients expressing this sentiment.2 Despite the increasing attention on pharmaceutical research for HS, the area of treatment remains the most pressing area that has yet to be fully addressed.

“The Hidradenitis Suppurativa Investigator Global Assessment…has been proposed as a measure to fulfill the global assessment domain, and to overcome limitations in existing measures used in clinical trials,” Garg and colleagues wrote.

Background and Findings

The investigators examined data retrospectively from a phase 2 clinical trial that was randomized, double-blind, placebo-controlled, and included an active-reference arm. The trial participants had been adults diagnosed with moderate-to-severe HS, and there were 88 in total.

Garg and colleagues sought to assess the validity, reliability, and responsiveness of the HS-IGA score and its association with other measures of HS severity and outcomes reported by patients. Their study population had been made up of randomized participants receiving at least 1 dose of the bimekizumab treatment and used a valid measurement of the primary efficacy variable.

The investigators’ statistical analysis was conducted through SAS software, and the convergent and divergent validity, test-retest reliability, and responsiveness were assessed using different correlation and statistical coefficients.

The study hypothesis was that the HS-IGA score would be more strongly associated with other measures of HS severity and less strongly correlated with measures of related but different patient-reported constructs such as pain and quality of life.

Overall, the research team reported that their results showed good convergent validity between HS-IGA and other assessment tools, strong test-retest reliability, and responsiveness to changes.

The HS-IGA score was associated with accurate Hidradenitis Suppurativa Clinical Response (HiSCR), showing that there was a 50%, 75%, and 90% reduction from baseline. Additionally, HS-IGA scores were associated with accurate Hidradenitis Suppurativa Clinical Response and HS-PhGA clear or minimal response at week 12.

Despite these positive findings for the HS-IGA, the tool was found to have shown low predictive validity as a measure of disease activity as far as outcomes reported by patients at 12 weeks.

Major Conclusions

In summary, HS-IGA score showed strong convergent validity with IHS4 and HS-PhGA, and divergent validity with a general skin disease quality of life (QoL) measure and global pain scales. The tool also showed very strong test-retest reliability, suggesting that raters can use the measure accurately.

Additionally, it showed responsiveness to changes when compared to HiSCR, and aligned most closely with HiSCR-90, as confirmed by the AUC analysis. However, the lack of agreement between HS-IGA and HiSCR-90 was primarily due to false-positive results in HS-IGA, possibly resulting from the limitations of HiSCR assessment.

Despite these facts, the investigators also found that the HS-IGA had low predictive validity with DLQI, a general skin disease QoL measure, and changes in patient-reported outcomes were not statistically significant at week 12 for HS-IGA responders vs nonresponders, as expected given that PROs focus on broader concepts of HS beyond just disease activity.


  1. Garg A, Zema C, Ciaravino V, et al. Validation of the Hidradenitis Suppurativa Investigator Global Assessment: A Novel Hidradenitis Suppurativa–Specific Investigator Global Assessment for Use in Interventional Trials. JAMA Dermatol. Published online April 26, 2023. doi:10.1001/jamadermatol.2023.0797.
  2. Garg A, Neuren E, Cha D, et al. Evaluating patients’ unmet needs in hidradenitis suppurativa: Results from the Global Survey Of Impact and Healthcare Needs (VOICE) Project. J Am Acad Dermatol. 2020;82(2):366-376. doi:10.1016/j.jaad.2019.06.1301.
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