Fig. 2

Flow diagram of natural language processing-augmented surveillance algorithm for deep surgical site infections

NLP: natural language processing; SSI: surgical site infection.

Schematic overview of the original semi-automated algorithm comprised of structured data (grey frame), augmented with unstructured data from clinical notes (blue frame).

Admissions: Length of stay of index admission ≥ 14 days or 1 readmission to original department or in-hospital mortality within follow-up (FU) time (= 45 days after surgery).

Re-surgery: ≥1 reoperation by original surgery specialty after the index surgery but within FU time.

Radiology: ≥1 orders for CT scan within FU time.

Antibiotics: ≥3 consecutive days of antibiotics (ATC J01) within FU time, starting from day 2 (index surgery = day 0).

Fulfilling 2–4 of the above components classifies surgery as high probability for deep SSI.