Biomarkers Capable to Early Predict Postoperative Complications: The Grail
We thank Labgaa et al. for their interest in our article and welcome the opportunity to respond. As they correctly point out patients undergoing laparoscopic abdominal surgery have an improved outcome compared with patients with open surgery1. This may be the result of a superior preservation of immune function, measured by higher human leucocyte antigen-DR expression on monocytes after laparoscopic surgery.2 Similarly, one might argue that laparoscopic surgery is associated with reduced postoperative levels of IL-6. Although prior reports have shown that levels of IL-6 on day 1 were similar in patients randomized to open or laparoscopic colorectal surgery if treated according to a fast-track protocol.2,3 Labgaa et al. suggest that including the surgical approach (laparoscopic vs open) in multivariate analysis may have changed the results of our study.4 In our study population, 69 (51%) patients had laparoscopic surgery and 66 (49%) patients underwent an open procedure. In univariate analysis, open surgery was not associated with an increased risk of postoperative complications (odds ratio: 1.4, 95% confidence interval: 0.6–2.9, P = 0.433). After adding the surgical approach to the multivariate regression model a high IL-6 remained independently associated with the occurrence of postoperative complications (adjusted odds ratio: 3.1, 95% confidence interval: 1.2–8.2; P = 0.001).
It is true that IL-6 is an inflammatory biomarker that is currently not routinely used in clinical practice. However, this should not preclude its use. Levels of IL-6 increase rapidly and peak after 24 hours, followed by levels of CRP peaking after 48 hours.5 As a result, IL-6 may facilitate earlier discrimination between patients with and without an increased risk of postoperative complications than CRP, as is shown by the results of our study. The analytic variance of IL-6 is equal to the analytic variance of high-sensitivity CRP measurements.6
We recognize that at this time an IL-6 assay is more expensive than a CRP assay. Nevertheless, if this facilitates early prevention or detection of postoperative complications the net health care costs are likely to be reduced.