Is C-Reactive Protein (CRP) level measurement recommended on the first postoperative day?

From the Guidelines

Routine measurement of C-reactive protein (CRP) levels the day after surgery is generally not recommended for all patients. CRP is an acute phase reactant that rises in response to inflammation, infection, or tissue damage, and while it does increase after surgical procedures, this elevation is expected and not necessarily indicative of complications 1. The CRP level typically peaks 48-72 hours after surgery, making measurements on the first postoperative day less informative than those taken later.

Key Points to Consider

• CRP testing should be reserved for cases where there is clinical suspicion of postoperative infection or inflammatory complications, such as persistent fever, unexplained tachycardia, or other signs of systemic inflammatory response.
• In these situations, CRP can be useful as part of a comprehensive assessment, particularly when trended over time rather than as a single value 1.
• For most uncomplicated surgeries, clinical assessment including vital signs, wound examination, and patient symptoms provides more valuable information than routine CRP measurement in the immediate postoperative period.
• A study published in 2017 found that CRP has sensitivity of 73% to 91% and specificity of 81% to 86% for the diagnosis of prosthetic knee infection when a cutoff of 13.5 mg/L or more is used 1.

Clinical Application

• The use of CRP levels in the diagnosis of postoperative infection or inflammatory complications should be guided by clinical judgment and suspicion, rather than routine measurement.
• Other diagnostic tools, such as joint aspiration and imaging studies, may be more useful in certain situations, and should be considered in conjunction with CRP levels 1.

From the Research

CRP Levels After Surgery

• CRP levels are not recommended to be checked the day after surgery, as they can be elevated due to the surgical trauma itself, rather than an infection 2.
• Studies have shown that CRP levels peak on the second or third day after surgery, and then decrease, making it difficult to use as a tool to screen for infection in the first few days after surgery 2, 3.
• However, CRP levels can be useful in diagnosing infection after the first three postoperative days, and in monitoring response to treatment 2.
• A study found that CRP levels increased in the first week after major surgery, but to a much larger extent in infected patients than in non-infected patients 3.
• Another study found that a cut-off level of 96 mg/L after the fourth day of surgery could be used to aid in early detection of surgical complications, such as deep wound infection 4.
• A systematic review and pooled-analysis found that postoperative CRP levels on the third day could be used as a predictor for major complications after major abdominal surgery, with proposed cut-offs for safe discharge and early identification of patients at risk for complications 5.

Interpretation of CRP Levels

• CRP levels should be interpreted with caution, taking into account the type of surgery, the extent of surgical trauma, and the presence of co-morbidities 2, 6.
• A study found that CRP levels were higher in patients with co-morbidity, and that the peak CRP level was higher and occurred later in patients with a high pre-operative CRP 2.
• Another study found that CRP levels were lower in super-super obese patients, and higher in patients who underwent gastric bypass procedures 6.
• The cut-off values for CRP levels can vary depending on the study and the population, but a common cut-off value is around 100 mg/L 3, 4, 5.