A systematic review of core outcomes reported in boys and men with Klinefelter syndrome

Klinefelter syndrome (XXY) has a wide range of presentations and health consequences. The aim of this systematic review was to identify potential core outcomes reported in males with XXY. Systematic searches of PubMed, Science Direct, and Cochrane were performed to source studies. The inclusion criteria were studies involving males with KS with any intervention, comparison, or outcome, with separate searches for studies reporting on children <16 years of age and for adults ≥16 years of age. For children <16 years old, 56 studies met the eligibility criteria. Thirty-seven (66%) studies reported anthropometric measurements and physical characteristics. Behavioural, cognitive developmental and psychiatric outcomes were also commonly reported (27, 48%) as were biochemical results in 27 (48%) studies. Other outcomes included presence of co-morbidities (16, 29%) and fertility outcomes (10, 18%). In the studies focusing on individuals ≥16 years of age, 183 studies met the eligibility criteria. Outcomes relating to biochemistry, physical characteristics, fertility and occurrence of co-morbidities were reported in 118 (64%), 89 (49%) 65 (36%) and 62 (34%) studies respectively. Quality of life was reported least frequently in only 2 (4%) paediatric studies and 5 (3%) of adult studies. The present study highlights the variety of outcomes studied in boys and men with KS. These results can support the development of age-specific core outcome sets for clinical research to promote homogeneity and to aid standardised data collection.