Day-2 CRP below 100 mg/L: a leak-exclusion threshold for earlier discharge

Design

Two-cohort multicentre diagnostic accuracy study

Population

614 patients after elective colon cancer resection with primary anastomosis (401 test, 213 validation)

Primary outcome

Anastomotic leak, Clavien–Dindo grade ≥3

Effect

Day-2 CRP <100 mg/L NPV 98.8% (test) and 99.0% (validation)

This Danish multicentre diagnostic accuracy study tested whether a C-reactive protein below 100 mg/L on postoperative day 2, rather than the commonly used day-3 threshold, could exclude anastomotic leak after elective colon cancer resection with primary anastomosis. Leak was defined as Clavien–Dindo grade 3 or above. There was a test cohort of 401 and a validation cohort of 213.

Leak occurred in about 4–5% overall. A day-2 CRP below 100 was seen in 60% and 46% of patients, and in them leak occurred in only 1.3% and 1.0% — negative predictive values of 98.8% and 99.0%. Above 100, leak rates rose to about 8%. In those patients, a day-3 CRP lower than day 2 (ratio below 1) identified a further low-risk group. With the two steps together, nearly 90% could be discharged by day 2 or 3 with leak risk near 1%.

Within an enhanced recovery pathway this gives a simple, testable rule for earlier discharge. It applies to elective colon cancer surgery, not rectal resection or emergency work, and it rests on clinical review alongside the number. Units adopting it should audit their own leak and readmission rates.

• Check CRP on day 2 after elective colon cancer resection within an enhanced recovery pathway.
• Consider discharge on day 2 or 3 for well patients with a day-2 CRP below 100 mg/L.
• Recheck on day 3 when day 2 is 100 or above; a falling value identifies more low-risk patients.
• Do not apply the threshold to rectal or emergency resections, which were not studied.
• Audit local leak and readmission rates if the pathway is introduced.

Why it matters

It moves a widely used safety threshold one day earlier, matching how enhanced recovery already discharges.

Don't overread it

This applies to elective colon cancer resections only; about 1 in 100 low-CRP patients still had a leak.

The statistics, in plain English

A negative predictive value of 99% means that of 100 patients with a low day-2 CRP, about one turned out to have a leak. It does not mean the test catches 99% of leaks. Validation in a second cohort with a similar result strengthens confidence, but both were Danish and elective.

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