[Methods to determine minimal clinically important difference].

There are 4 methods to determine a minimal clinically important difference (MCID) currently, namely anchor-based method, distribution-based method, opinion-based method, and literature review. The anchor-based method offers the clinical significance of MCID, but it does not consider the measurement error. The anchor-based method is limited due to difficulty to obtained a suitable anchor in most cases, and variation of MCID with the anchor. The distribution-based method takes measurement error into account, and is easily implemented. The distribution-based method can not provide the clinical explanation of MCID, and the MCID from different samples might differ from each other. There is no golden criterion to judge MCID by distribution-based method so far. The opinion-based method and literature review are based on the opinions of experts and the published literature, respectively. They are usually regarded as a supplement to anchor-based method and distribution-based method. It is suggested that anchor-based method, distribution-based method, and opinion-based method should be used together when determining a MCID.