A day-2 CRP below 100 mg/L makes a leak after colon resection unlikely

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 needing intervention (Clavien-Dindo 3 or above)

Effect

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

This diagnostic accuracy study used two multicentre cohorts of elective colon cancer resections with primary anastomosis: a test cohort of 401 and a validation cohort of 213. Anastomotic leak was defined as one needing intervention (Clavien-Dindo grade 3 or above). A CRP below 100 mg/L on day 3 is widely used to exclude leak; the question was whether day 2 works too.

Leaks occurred in 4.0% and 4.7%. A day-2 CRP below 100 mg/L was present in 60% and 46% of patients, and only 1.3% and 1.0% of them leaked, giving negative predictive values of 98.8% and 99.0%. Among patients above the threshold, about 8% leaked. For those patients, a day-3 CRP lower than day 2 identified a further low-risk group (negative predictive values 98.9% after minimally invasive and 97.9% after open surgery). With this two-step approach, almost 90% could go home by day 2 or 3 with leak risk near 1%.

A low CRP lowers the risk; it does not remove it, and clinical review still decides discharge. It also applies to colon, not rectal, resections, and the cohorts had a low baseline leak rate. Units with higher leak rates should expect a lower negative predictive value.

• Consider checking CRP on day 2 after elective colon resection within an ERAS pathway.
• If CRP is below 100 mg/L and the patient is well, consider discharge on day 2 or 3 with clear return advice.
• If CRP is 100 mg/L or above, repeat on day 3 and look for a fall before planning discharge.
• Do not let a reassuring CRP override tachycardia, fever, pain or failure to progress.
• Do not apply this threshold to rectal resections, where it was not studied.

Why it matters

The common day-3 CRP rule is a day later than ERAS patients are often ready to leave; this offers an earlier, validated check.

Don't overread it

A negative predictive value depends on how common leaks are; in a unit with more leaks than these cohorts, a low CRP is less reassuring.

The statistics, in plain English

A negative predictive value of about 99% means that of 100 patients with a low day-2 CRP, about one went on to leak. Because leaks were uncommon here (about 4 in 100), the figure would fall where leaks are more frequent. The day-3 ratio results come from combining both cohorts rather than a separate validation.

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