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.
Veterans Administration Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Code 111-G, Los Angeles, CA 90064, USA. karl.lorenz@med.va.gov
Karl A
KA
Lorenz
Cathy D
CD
Sherbourne
Lisa R
LR
Shugarman
Lisa V
LV
Rubenstein
Li
L
Wen
Angela
A
Cohen
Joy R
JR
Goebel
Emily
E
Hagenmeier
Barbara
B
Simon
Andy
A
Lanto
Steven M
SM
Asch
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