Utility of Postoperative D-dimer Thresholds and Caprini Score in Predicting Deep Venous Thrombosis Following Cranial and Spinal Neurosurgery

Abstract Background and Objectives: Deep venous thrombosis (DVT) is a significant cause of morbidity and mortality in neurosurgical patients. While Doppler ultrasound is the gold standard for DVT diagnosis, its use is limited in resource-constrained settings. Traditional d-dimer thresholds (500 ng/mL), primarily validated in European and North American populations, may not account for physiological variations across ethnic groups, especially within the Sub-Saharan populations, who typically exhibit higher physiological baseline levels. Additionally, physiological d-dimer elevations in the early postoperative period complicate its use for DVT prediction. This study aimed to determine postoperative d-dimer thresholds for predicting DVT in cranial and spinal surgery patients, establish levels that distinguish physiological elevations from true DVT, and evaluate the utility of combining the Caprini score with d-dimer levels. Methodology: A prospective cohort study was conducted at a tertiary neurosurgical centre over 12 months. Participants included patients aged ≥40 undergoing elective cranial or spinal surgeries, excluding those with preoperative DVT, anticoagulation therapy, or other d-dimer-elevating conditions. D-dimer levels and Caprini scores were measured preoperatively and on postoperative days 1, 3, and 7. Doppler ultrasound scans served as the gold standard for DVT diagnosis. Statistical analyses included ROC curves and Youden index to determine optimal d-dimer thresholds. Results: Of 67 patients, 12 (17.9%) developed DVT. For cranial surgeries, physiological postoperative d-dimer elevations in DVT-negative patients remained stable (median: 4100–4350 ng/mL), while DVT-positive patients showed progressive increases (peaking at 8600 ng/mL on day 3). Optimal thresholds to distinguish DVT were 5020 ng/mL (day 1), 7450 ng/mL (day 3, AUROC 0.958), and 5770 ng/mL (day 7). For spinal surgeries, DVT-negative patients maintained low levels (2300–2550 ng/mL), whereas DVT-positive patients had early peaks (9055 ng/mL on day 1). Thresholds were 7540 ng/mL (day 1, AUROC 0.96), 5830 ng/mL (day 3), and 4520 ng/mL (day 7). Combining Caprini scores with d-dimer did not improve diagnostic accuracy over d-dimer alone. Conclusions: Population-specific d-dimer thresholds (7450 ng/mL on day 3 for cranial surgeries and 7540 ng/mL on day 1 for spinal surgeries) effectively predicted DVT. Combining Caprini scores with d-dimer testing did not offer any advantage over using d-dimer alone for predicting lower limb DVT.