Purpose: We examined the validity of the Childhood Asthma Control Test (C-ACT) and identified recommended thresholds for uncontrolled asthma in children from varying backgrounds.

Methods: A systematic literature review was performed utilizing PubMed, Ovid Medline, SCOPUS, CINAHL, and conference proceedings. Studies were included if they enrolled children, had a primary outcome of asthma control, examined test validity or psychometrics, and utilized the C-ACT. Along with study design and demographic data, we extracted all outcomes and comparisons used to validate the C-ACT. We evaluated risk of bias using the COSMIN Risk of Bias tool. Our protocol was registered with PROSPERO (CRD42020211119).

Results: Of 4924 records screened, 28 studies were included. Studies were conducted internationally and published between 2007 and 2018. Average number of enrolled participants was 193 (SD = 155, range = 22-671). Ten studies calculated Cronbach's α (mean [SD] = 0.78(0.05), range = 0.677-0.83). Thirteen studies recommended cut-offs for uncontrolled asthma (≤18-≤24). Nine studies found significant agreement or correlation between C-ACT and Global Initiative for Asthma guidelines/physician assessment of asthma control (correlation coefficients range = 0.219-0.65). Correlation coefficients between C-ACT and spirometry were <0.6 in five of six studies that included spirometry. Kappa values for C-ACT and various spirometry measurements ranged 0.00-0.34.

Conclusions: The C-ACT showed good internal consistency and mixed levels of agreement and correlation with various clinical asthma measures. Recommended cut-offs for asthma control varied and had no consistent relationship with nationality, race, ethnicity, or language. Few studies examined cross-cultural validity and multiple populations remain under-studied.