The added value of extending the EQ-5D-5L with an itching item for the assessment of health-related quality of life of burn patients: an explorative study

Abstract Introduction Health-related quality of life (HRQL) is an important outcome in burn care and research. An advantage of a generic HRQL instrument, like the EQ-5D, is that it enables comparison of outcomes with other conditions and the general population. However, the downside is that it does not include burn specific domains, like scar issues or itching. Adding extra items to a generic instrument might overcome this issue. This study explored the potential and added value of extending the EQ-5D-5L with a burn-specific item, using an itching item as an example. Methods The EQ-5D-5L and the Patient and Observer Scar Assessment Scale (POSAS) was completed by adult patients 5–7 years after their burn injury. The separate POSAS itching item was used to study the added value of an itching item for the EQ-5D-5L. The EQ-5D-5L + Itching was created by adding the POSAS itching item to the EQ-5D-5L. Five psychometric properties were compared between EQ-5D-5L and EQ-5D-5L + Itching: distribution (e.g. ceiling), informativity cf. Shannon’s indices, convergent validity, dimension dependency, and explanatory power respectively. Results A total of 245 patients were included, of whom 48% reported any itching on the POSAS. Adding an itching item to the EQ-5D-5L decreased the ceiling effect, and resulted in increased absolute informativity (H’ = 4.76 vs. H’ = 3.64) and relative informativity (J’ = 0.34 vs. J’ = 0.31). The extra itching item decreased the convergent validity (Spearman’s rank correlation coefficient = −0.51 vs. −0.59). Mutual dependency of dimensions existed, showing that all other items were dominant over the itching item. Adding the itching item to the standard EQ-5D-5L barely improved explanatory power (49.3% vs. 49.0%). Conclusions Present study showed that adding a burn-specific item to the EQ-5D-5L is possible and has potential. However, 5 to 7 years after injury, adding an itching item to the EQ-5D-5L provides only some additional information; the gain in terms of added value is relatively small. Apart from instances were itching information is specifically needed, there is not a strong case for adding an itching item to the EQ-5D-5L for long-term (>5 yr after burns) HRQL assessment in burn patients. Shorter after burns the added value might be greater and we recommend to explore this potential in future studies, ideally on multiple timepoints post-burn.