TY - JOUR AU - Farzanfar, Delaram AU - Abumuamar, Asmaa AU - Kim, Jayoon AU - Sirotich, Emily AU - Wang, Yue AU - Pullenayegum, Eleanor PY - 2017 DA - 2017/09/06 TI - Longitudinal studies that use data collected as part of usual care risk reporting biased results: a systematic review JO - BMC Medical Research Methodology SP - 133 VL - 17 IS - 1 AB - Longitudinal studies using data collected as part of usual care risk providing biased results if visit times are related to the outcome of interest. Statistical methods for mitigating this bias are available but rarely used. This lack of use could be attributed to a lack of need or to a lack of awareness of the issue. SN - 1471-2288 UR - https://doi.org/10.1186/s12874-017-0418-1 DO - 10.1186/s12874-017-0418-1 ID - Farzanfar2017 ER -