Stubbs, D; University Division of Anaesthesia, Cambridge, United Kingdom
Grimes, L;  Ercole, A;

A systematic review. PLoS ONE 15(2): e0226480

RESEARCH ARTICLE

Introduction
Cardiopulmonary exercise testing (CPET) is widely used within the United Kingdom for pre-
operative risk stratification. Despite this, CPET’s performance in predicting adverse events
has not been systematically evaluated within the framework of classifier performance.
Methods
After prospective registration on PROSPERO (CRD42018095508) we systematically identi-
fied studies where CPET was used to aid in the prognostication of mortality, cardiorespira-
tory complications, and unplanned intensive care unit (ICU) admission in individuals
undergoing non-cardiopulmonary surgery. For all included studies we extracted or calcu-
lated measures of predictive performance whilst identifying and critiquing predictive models
encompassing CPET derived variables.
Results
We identified 36 studies for qualitative review, from 27 of which measures of classifier per-
formance could be calculated. We found studies to be highly heterogeneous in methodology
and quality with high potential for bias and confounding. We found seven studies that pre-
sented risk prediction models for outcomes of interest. Of these, only four studies outlined a
clear process of model development; assessment of discrimination and calibration were per-
formed in only two and only one study undertook internal validation. No scores were exter-
nally validated. Systematically identified and calculated measures of test performance for
CPET demonstrated mixed performance. Data was most complete for anaerobic threshold
(AT) based predictions: calculated sensitivities ranged from 20-100% when used for predict-
ing risk of mortality with high negative predictive values (96-100%). In contrast, positive
predictive value (PPV) was poor (2.9-42.1%). PPV appeared to be generally higher for
cardiorespiratory complications, with similar sensitivities. Similar patterns were seen for the
association of Peak VO2 (sensitivity 85.7-100%, PPV 2.7-5.9%) and VE/VCO2 (Sensitivity
27.8%-100%, PPV 3.4-7.1%) with mortality.
Conclusions
In general CPET’s ‘rule-out’ capability appears better than its ability to ‘rule-in’ complica-
tions. Poor PPV may reflect the frequency of complications in studied populations. Our cal-
culated estimates of classifier performance suggest the need for a balanced interpretation
of the pros and cons of CPET guided pre-operative risk stratification