Content validation of the Spanish version of the Long-term Quality of Life Instrument for long-term female breast cancer survivors

Background: The quality of life of women affected by breast cancer diagnosed 5 or more years ago has been relatively unexplored in Spain: there are no instruments for its measurement validated. The objective of the study is to translate into Spanish, culturally adapt and examine the content validity of the Spanish version of the Long-Term Quality of Life Instrument (LTQL). Methods: The initial translation was performed by two translators with Spanish as their mother tongue carried out the translation of the questionnaire, obtaining two initial versions in Spanish (T1 and T2). An analysis of the results and elaboration of a single preliminary version in Spanish (T-1-2) were performed. The retro-translation was performed by two translators with English as their mother tongue not familiar with the original version translated the joint version (T-1-2) back into the original language (RT1 and RT2) to identify inconsistencies. Finally. a final version of the questionnaire was obtained. For content validation a committee of experts (seven women affected by breast cancer) assessed the degree of clarity, accuracy and understanding of each of the items in the questionnaire translated into Spanish, and calculated the content validity index (CVI) of the questionnaire according to Lawshe and Tristan. Results: The LTQL questionnaire %Nils translated into Spanish with a low discrepancy between translators. An adequate CVI higher than 0.58 was obtained in clarity (0.95), precision (0.93), comprehension (0.91) and relevance (0.72). Conclusions: The LTQL is a useful questionnaire in the health field for the assessment of quality of life of women survivors of long-term breast cancer.