How reliable is pain as the fifth vital sign?
BACKGROUND
Although many health care organizations require routine pain screening (eg, "5th vital sign") with the 0 to 10 numeric rating scale (NRS), its accuracy has been questioned; here we evaluated its accuracy and potential causes for error.


METHODS
We randomly surveyed veterans and reviewed their charts after outpatient encounters at 2 hospitals and 6 affiliated community sites. Using correlation and receiver operating characteristic analysis, we compared the routinely measured "5th vital sign" (nurse-recorded NRS) with a research-administered NRS (research-recorded NRS) and the Brief Pain Inventory (BPI).


RESULTS
During 528 encounters, nurse-recorded NRS and research-recorded NRS correlated moderately (r = 0.627), as did nurse-recorded NRS and BPI severity scales (r = 0.613 for pain during the last 24 hours and r = 0.588 for pain during the past week). Correlation with BPI interference was lower (r = 0.409). However, the research-recorded NRS correlated substantially with the BPI severity during the past 24 hours (r = 0.870) and BPI severity during the last week (r = 0.840). Receiver operating characteristic analysis showed similar results. Of the 98% of cases where a numeric score was recorded, 51% of patients reported their pain was rated qualitatively, rather than with a 0 to 10 scale, a practice associated with pain underestimation (chi2 = 64.04, P < .001).


CONCLUSIONS
Though moderately accurate, the outpatient "5th vital sign" is less accurate than under ideal circumstances. Personalizing assessment is a common clinical practice but may affect the performance of research tools such as the NRS adopted for routine use.
Lorenz
Karl A
KA
Veterans Administration Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Code 111-G, Los Angeles, CA 90064, USA. karl.lorenz@med.va.gov
Sherbourne
Cathy D
CD
Shugarman
Lisa R
LR
Rubenstein
Lisa V
LV
Wen
Li
L
Cohen
Angela
A
Goebel
Joy R
JR
Hagenmeier
Emily
E
Simon
Barbara
B
Lanto
Andy
A
Asch
Steven M
SM
D000368:Aged; D002140:California / Q000453:epidemiology; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000175:diagnosis* / Q000453:epidemiology / Q000451:nursing; D010147:Pain Measurement / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D014728:Veterans / Q000706:statistics & numerical data