May's Paper of the Month looks at a study to develop a disease-specific measurement instrument that can accurately measure QoL for patients with cryptoglandular anal fistula.

The development of a cryptoglandular anal fistula quality of life scale (AF-QoL)
Nusrat Iqbal, Laith Alrubaiy, Ailsa Hart , Rachel Siviter, Lynsay Wilson, Phil Tozer
Colorectal Disease. 18 Feb 2024.

What is known about the subject?

The best way to measure cryptoglandular anal fistula treatment success is by determining quality of life (QoL) outcomes. However, there are no high quality questionnaires that give a holistic assessment of a patient's condition. Only in a minority of studies focusing on anal fistula management measure quality of life (QoL), and when they do, they use generic instruments. There is a clear need for disease-specific instruments but the very few that exist show a lack of patient involvement. This, by definition, means that they lack content validity and are at risk of research bias.

What the study adds?

The article describes the development of a patient-centered, disease-specific, and comprehensive instrument to measure QoL among patients with cryptoglandular anal fistulas.

Qualitative interviews were conducted to generate the questions, and a 44-item draft was refined through cognitive interviews and assessments by independent experts. Stepwise regression from this initial 44-item draft to a 22-item scale was performed., The developed score was tested for reliability, responsiveness, and interpretability using psychometric analysis, test-retest analysis, and psychometric analysis.

Experts in patient reported outcome measure development directing methodology ensured that Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) standards were followed.

The instrument finally includes 22 questions and is scored on a scale from 0 (worst possible outcome) to 100 (best possible outcome). It has acceptable internal consistency (Cronbach-α= 0.927), strong content and construct validity (correlation with Perianal Disease Activity Index= -0.713), as well as a strong reliability (Pearson correlation coefficient = 0.929, intraclass correlation= 0.865) and an acceptable responsiveness.

The initial analysis supports the validity of the tool, further prospective studies, conducted specifically on patients undergoing treatment resulting in a change in symptoms, could provide additional data to support the sensitivity of the instrument.

Implications for colorectal practice

A novel 22-item scale has been devised to assess the specific and direct impact of having a cryptoglandular anal fistula or its treatment on quality of life. The instrument demonstrates reliability, construct validity and internal consistency. Future studies should focus on assessing its measurement properties alongside other QoL instruments, and in determining reference values for the scale, from which the severity of QoL impact can be deduced.


  1. Iqbal N, Alrubaiy L, Hart A, et al: The development of a cryptoglandular anal fistula quality of life scale (AF-QoL). Colorectal Dis 26(4):716-725, 2024
  2. Iqbal N, Shar R, Alrubaiy L, Tozer P: Do Patient-Reported Quality-of-Life (QoL) Scales Provide an Adequate Assessment of Patients with Cryptoglandular Anal Fistulae? A Systematic Review of Measurement Instruments and Their Content Validity. Clin Pract 12(4):628-639, 2022
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