**5. Summary**

The available data on HRQOL in patients under OL-HDF therapy is limited and of low quality. Most parallel-group randomized clinical trials on this subject demonstrate no or limited improvement in HRQOL associated with OL-HDF. However, several crossover studies support a beneficial role of OL-HDF in enhancing quality of life in these patients. The effect of online HDF on quality of life reported by clinical studies is variable. The inconsistency of these results is probably related to different methods used to assess quality of life, sample size, duration of study, and the different characteristics of the convective therapy utilized such as blood flow rate, vascular access type and type of the dialyzer, convection volume, and frequency of online HDF. The most widely used and tested method of assessing health-related quality of life in patients undergoing online HDF replacement therapy is Kidney Disease Quality of Life Short Form-36 (KDQOL-SF-36). It is easily administrable and has been vali‐ dated.

With the increased popularity of OL-HDF as a renal replacement therapy, larger better organized studies will probably become available in the future. Such studies, hopefully, will better clarify the issue.

### **Author details**

Samir H. Almueilo

Address all correspondence to: smueilo@uod.edu.sa

King Fahd Hospital of the University, University of Dammam, Alkhobar, Saudi Arabia
