Abdul Khairul Rizki Purba,1– 4 Christian F Luz,2 Riyanti R Wulandari,5 Ieneke van der Gun,2 Jan-Willem Dik,2 Alex W Friedrich,2 Maarten J Postma1,3,4,6 1Department of Health Sciences, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; 2University of Groningen, University Medical Center Groningen, Department of Medical Microbiology, Groningen, the Netherlands; 3Department of Pharmacology and Therapy, Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia; 4Unit of Pharmacotherapy, -Epidemiology and -Economics (PTE2), Department of Pharmacy, Faculty of Science and Engineering, University of Groningen, Groningen, the Netherlands; 5Department of Pharmacy, Dinas Kesehatan Kota Surabaya, Surabaya, Indonesia; 6Department of Economics, Econometrics and Finance, Faculty of Economics & Business, University of Groningen, Groningen, the NetherlandsCorrespondence: Abdul Khairul Rizki PurbaUniversitair Medisch Centrum Groningen, Hanzeplein 1, Groningen 9700RB, the Netherlands, Tel +62 81230019201Email khairul_purba@fk.unair.ac.idObjective: This study aimed to evaluate the impacts of deep surgical site infections (dSSIs) regarding hospital readmissions, prolonged length of stay (LoS), and estimated costs.Patients and Methods: We designed and applied a matched case–control observational study using the electronic health records at the University Medical Center Groningen in the Netherlands. We compared patients with dSSI and non-SSI, matched on the basis of having similar procedures. A prevailing topology of surgeries categorized as clean, clean-contaminated, contaminated, and dirty was applied.Results: Out of a total of 12,285 patients, 393 dSSI were identified as cases, and 2864 patients without SSIs were selected as controls. A total of 343 dSSI patients (87%) and 2307 (81%) controls required hospital readmissions. The median LoS was 7 days (P25-P75: 2.5– 14.5) for dSSI patients and 5 days (P25-P75: 1– 9) for controls (p-value: < 0.001). The estimated mean cost per ...