Development and validation of the symptom burden questionnaire for long covid (SBQ-LC): Rasch analysis

  1. Sarah E Hughes
  2. Shamil Haroon
  3. Anuradhaa Subramanian
  4. Christel McMullan
  5. Olalekan L Aiyegbusi
  6. Grace M Turner
  7. Louise Jackson
  8. Elin Haf Davies
  9. Chris Frost
  10. Gary McNamara
  11. Gary Price
  12. Karen Matthews
  13. Jennifer Camaradou
  14. Jane Ormerod
  15. Anita Walker
  16. Melanie J Calvert

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Abstract

Objective

To describe the development and validation of a novel patient reported outcome measure for symptom burden from long covid, the symptom burden questionnaire for long covid (SBQ-LC).

Design

Multiphase, prospective mixed methods study.

Setting

Remote data collection and social media channels in the United Kingdom, 14 April to 1 August 2021.

Participants

13 adults (aged ≥18 years) with self-reported long covid and 10 clinicians evaluated content validity. 274 adults with long covid field tested the draft questionnaire.

Main outcome measures

Published systematic reviews informed development of SBQ-LC’s conceptual framework and initial item pool. Thematic analysis of transcripts from cognitive debriefing interviews and online clinician surveys established content validity. Consensus discussions with the patient and public involvement group of the Therapies for Long COVID in non-hospitalised individuals: From symptoms, patient reported outcomes and immunology to targeted therapies (TLC Study) confirmed face validity. Rasch analysis of field test data guided item and scale refinement and provided initial evidence of the SBQ-LC’s measurement properties.

Results

SBQ-LC (version 1.0) is a modular instrument measuring patient reported outcomes and is composed of 17 independent scales with promising psychometric properties. Respondents rate their symptom burden during the past seven days using a dichotomous response or 4 point rating scale. Each scale provides coverage of a different symptom domain and returns a summed raw score that can be transformed to a linear (0-100) score. Higher scores represent higher symptom burden. After rating scale refinement and item reduction, all scales satisfied the Rasch model requirements for unidimensionality (principal component analysis of residuals: first residual contrast values <2.00 eigenvalue units) and item fit (outfit mean square values within 0.5 -1.5 logits). Rating scale categories were ordered with acceptable category fit statistics (outfit mean square values <2.0 logits). 14 item pairs had evidence of local dependency (residual correlation values >0.4). Across the 17 scales, person reliability ranged from 0.34 to 0.87, person separation ranged from 0.71 to 2.56, item separation ranged from 1.34 to 13.86, and internal consistency reliability (Cronbach’s alpha) ranged from 0.56 to 0.91.

Conclusions

SBQ-LC (version 1.0) is a comprehensive patient reported outcome instrument developed using modern psychometric methods. It measures symptoms of long covid important to people with lived experience of the condition and may be used to evaluate the impact of interventions and inform best practice in clinical management.

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  1. Version published to 10.1136/bmj-2022-070230
  2. ScreenIT

    SciScore for 10.1101/2022.01.16.22269146: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Statistical Analyses: STATA (Version 16) was used to clean and prepare the data and SPSS (Version 28.0) was used for descriptive data analyses.
    STATA
    suggested: (Stata, RRID:SCR_012763)
    SPSS
    suggested: (SPSS, RRID:SCR_002865)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The use of social media to recruit participants meant it was not possible to confirm representativeness of the field test sample and is a limitation of this study. The relatively low completion rate suggested potential field test participants (i.e., possibly individuals experiencing higher levels of symptom burden, for example, symptoms such as fatigue or cognitive dysfunction) may have been deterred by the effort required to complete the SBQ™-LC or lacked sufficient incentive to participate. As such, the level of symptom burden captured in the field test may not reflect accurately the wider experience of Long COVID patients. Lastly, despite attempts to sample purposively for maximum variation, the demographics of the content validation study sample were highly skewed towards white (100%) females (76.9%). Further validation, undertaken as part of the TLC study which will prospectively target higher representation from ethnic minority groups, is planned and aims to confirm these findings. Further research is also needed to evaluate the SBQ™-LC using traditional psychometric indicators including test-retest reliability, construct validity, responsiveness, and measurement error. Studies to explore the feasibility and acceptability of the SBQ™-LC for use in clinical settings are also needed. The SBQ™-LC is currently available in UK English as an ePRO and in paper form. Linguistic and cross-cultural validation studies will ensure its generalizability outside of the UK and make tra...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

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  3. Version published to 10.1101/2022.01.16.22269146v1 on medRxiv