The relationship between ambulatory step activity, self-reported physical functioning and standardised timed walking in patients with hematological malignancies

Purpose. 
This cross-sectional study investigated the degree of association between the results of ambulatory step activity monitoring (SAM), self-reported physical functioning (SRPF) and the 6-minute standardised walking test (6-MWT) in cancer patients with haematological malignancies.

Method. 
Assessments of ambulatory SAM, SRPF and 6-MWT were assessed in 102 patients up to 122 days (mean 78 ± 35) after haematopoietic stem cell transplantation (HSCT). To determine the association between measures of walking, the Pearson product moment correlation coefficient (r) including the 95%CI and the r2 were calculated. Simple linear regression analyses were performed to estimate the ambulatory step activity from SRPF and the 6-MWT.

Results. 
The average age was 47 years (±12) and body mass index 23.4 (±4). The correlations were low between ambulatory SAM outputs and SRPF (ranging from −0.32 to 0.34, p < 0.01), and very low between SAM outputs and 6-MWT, (ranging from 0.21 to 0.24). The correlation between SRPF and the 6-MWT was low (0.33, p < 0.01). The correlation between SRPF and the 6-MWT was low (0.33, p < 0.01). The 95%CIs were quite narrow around r. The shared variance (r2) between the SAM and SPPF ranged between 4% and 11% and the shared variance between the SAM and 6-MWT ranged between 0.5% and 18%. Linear regression yielded weak relationships and large standard errors of estimate between the SAM, SRPF and 6-MWT.

Conclusions. 
SRPF and the 6-MWT do not reflect daily walking activity. In clinical use (e.g. to evaluate the effects of a rehabilitation program), ambulatory step activity outputs can be considered an additional outcome to assess day-to-day walking activity in patients with haematological cancer after HSCT.