Abstract
Background
Below-knee amputation (BKA) is frequently performed but carries a meaningful risk of proximal re-amputation. Transcutaneous oxygen pressure (TcPO2) can aid prediction for re-amputation, yet its accuracy and availability are limited by patient and technical factors. Postoperative inflammatory testing also lacks standard guidelines and adds cost. The delta neutrophil index (DNI) is automatically derived from a routine complete blood count without additional testing or cost. In this study, we aimed to evaluate whether postoperative DNI predicts early conversion to above-knee amputation (AKA) after non-traumatic BKA.
Methods
We retrospectively evaluated all BKA procedures performed in the Orthopedic Surgery Department at Wonju Severance Christian Hospital between 2011 and 2021. These procedures were identified using the Current Procedural Terminology code 27880. The characteristics of patients requiring AKA within 30 days after non-traumatic BKA (AKA group) were compared to those of patients who did not require further amputation (non-AKA group). The demographic characteristics, laboratory findings, and clinical outcomes of patients who underwent non-traumatic BKA were examined. Moreover, a multivariable logistic regression model and receiver operating characteristic (ROC) curve were developed to evaluate the prognostic value of the DNI for early AKA.
Results
In total, 130 cases of non-traumatic BKA were identified. Proximal amputations within the first 30 postoperative days (PODs) were performed in 13 patients. Participants in the AKA group had significantly higher DNI on POD 1 compared with the non-AKA group (median [interquartile range], 2.3 [1.3–4.1] vs. 1.0 [0–2.3]; p = 0.022). In the multivariate analysis, the odds ratio for early AKA according to the DNI on POD 1 was 1.46 (95% CI, 1.03–2.08), and the area under the ROC curve of the DNI on POD 1 was 0.7 (with an optimal cutoff value of 1.95, a sensitivity of 0.73, and a specificity of 0.69).
Conclusions
In patients aged < 65 years undergoing BKA, POD 1 DNI—available from routine complete blood counts—can be used as a first-line screen and adjunctive prognostic marker to identify a higher risk of ipsilateral AKA within 30 days. Larger cohorts are needed to confirm thresholds and pathways.
Keywords: Diabetic foot, Neutrophils, Surgical amputation, Prognosis, Complete blood count
Lower-extremity amputation is commonly performed in patients with diabetes mellitus (DM), peripheral arterial occlusive disease (PAOD), and trauma.1) However, determining the level of amputation is extremely challenging, especially in non-traumatic cases in which lower-extremity amputation is required due to complications of DM or PAOD.2) The main considerations for amputation are the preservation of mobility and quality of life,3,4,5) as well as minimizing the risk of complications leading to re-amputation.6)
While distal amputation can preserve mobility, it increases the risk of treatment failure.7,8) Moreover, if distal amputation results in additional proximal amputations owing to treatment failure, it adversely affects the patient’s prognosis.9,10) The cumulative incidence of ipsilateral reamputation in patients with arteriosclerotic and diabetic gangrene requiring lower-extremity amputation is approximately 10%, 16%, and 18% at postoperative 1 month, 3 months, and 6 months, respectively.11) However, to our knowledge, few studies have assessed the risk factors associated with treatment failure and the possibility of reamputation.2,12) Moreover, transcutaneous oximetry, which is conventionally used to assess limb amputation prognosis, is often under- or over-estimated due to factors such as skin quality, room temperature, and electrode placement.13) Therefore, a more individualized and reliable approach is needed to better understand post-amputation prognosis.
The delta neutrophil index (DNI) is the proportion of circulating immature granulocytes and can be obtained from the differences between the leukocyte subfractions measured in the myeloperoxidase and nuclear lobularity channels.14) An increase in the DNI reflects a state of left-shift leukocytosis and limited migration of mature neutrophils to the circulation due to the overproduction of cytokines and chemokines in the early stage of inflammation.15) Previous studies have reported that the DNI can be used as a prognostic factor for various conditions, such as sepsis16) and acute gastrointestinal disease,17) and for predicting the need for surgery in patients with foot and ankle infections.18)
Although several studies have investigated the risk of amputation in patients with DM and PAOD, few have evaluated the predictive factors for re-amputation in patients with non-traumatic lower-extremity amputation.2,12,19) Therefore, we evaluated the DNI as a cost-effective adjunctive marker for predicting additional proximal amputation in patients undergoing non-traumatic below-knee amputation (BKA). As DNI can be derived from routine complete blood count (CBC) without additional testing or cost, it may serve as a practical option to complement the current lack of reliable predictors for reamputation. Understanding the predictors of surgery can help prevent meaningless delays in further surgical intervention. Accordingly, we hypothesized that postoperative day (POD) 1 DNI20) would be associated with ipsilateral conversion to above-knee amputation (AKA) within 30 days after non-traumatic BKA. In this study, we aimed to evaluate whether postoperative DNI predicts early conversion to AKA after non-traumatic BKA.
METHODS
This study was approved by the Institutional Review Board of Wonju Severance Christian Hospital, Yonsei University Health System (IRB No. CR321153). The study design was a retrospective review, and the requirement for informed consent from patients was waived by the Institutional Review Board of Wonju Severance Christian Hospital, Yonsei University Health System. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Patient Selection and Data Collection
This retrospective study included all patients who underwent BKA in the Orthopedic Surgery Department at Wonju Severance Christian Hospital between January 2011 and December 2021. Patients who underwent BKA were identified using the Current Procedural Terminology code 27880. Those who underwent BKA due to diabetic foot and PAOD were included in this study. The exclusion criteria were: (1) BKA due to trauma and (2) missing DNI data on the operation date. Patients were grouped based on the primary outcome of AKA within 30 days after BKA: the AKA group (AKA ≤ 30 days) and the non-AKA group (no AKA within 30 days). Data regarding demographic characteristics (age, sex, smoking status [non-smoker vs. ex-smoker vs. current smoker], and alcohol consumption [heavy drinker vs. non-heavy drinker]), comorbidities (such as hypertension, DM, chronic kidney disease, liver cirrhosis, and PAOD), laboratory findings, clinical outcomes, and AKA within 30 days in patients undergoing non-traumatic BKA were retrospectively reviewed. A heavy drinker was defined as an individual with a history of alcohol-related issues such as alcoholic liver cirrhosis, psychiatric treatment for alcoholism, and alcoholic delirium.
DNI and Laboratory Outcomes
The aspartate transaminase (AST), alanine aminotransferase (ALT), C-reactive protein (CRP), serum creatinine, and serum albumin levels of the patients were assessed preoperatively. The white blood cell (WBC) count, hemoglobin (Hb) level, and DNI were determined preoperatively and on PODs 0, 1, and 6. The decision to use POD 1 as a key time point for the assessment of early postoperative prognosis using DNI was influenced by previous findings, such as those reported by Bang et al.,20) which demonstrated that the DNI on POD 1 was a significant predictor of mortality, with a high area under the receiver operating characteristic (ROC) curve (AUROC) of 0.887. The DNI was calculated using the following formula: DNI = (leukocyte subfraction assayed in the myeloperoxidase channel by cytochemical reaction) – (leukocyte subfraction assayed in the nuclear lobularity channel using the reflected light beam).14) At our institution, complete blood cell assays are conducted using a specific type of automated blood cell analyzer (ADVIA 120/212; Siemens), via which the DNI can be calculated rapidly without any additional cost. However, during the study period, postoperative CRP was not obtained routinely and was available in < 10 patients; therefore, postoperative CRP was not included in ROC or correlation analyses to avoid unstable estimates. All blood samples were collected in the morning, after a period of fasting.
Statistical Analysis
Continuous variables are presented as mean ± standard deviation or median values (interquartile range). To determine differences between the groups, Student independent t-test was used when the data were presented as mean ± standard deviation. The Mann-Whitney U-test was used when the data were presented as median values. Categorical variables were analyzed using either the chi-squared test or Fisher’s exact test. Multivariate logistic regression analysis was conducted to investigate whether the DNI was a prognostic factor for early AKA. Moreover, the multivariate analyses were performed with adjustments for age, sex, smoking status, and alcohol consumption. ROC curve analysis was performed, and the Liu method was used to estimate the optimal cutoff values of the WBC count, Hb level, and DNI.21) For all ROC figures in this manuscript, the diagonal 45° line denotes the no-discrimination reference (AUROC = 0.5). All statistical analyses were 2-tailed and were performed using Stata version 15.1 (Stata Corp.). The level of statistical significance was set at p < 0.05.
RESULTS
Study Population and Baseline Characteristics
In total, 160 patients underwent BKA at our hospital between January 2011 and December 2021. Among them, 23 patients who underwent BKA due to trauma and 7 with missing DNI data on the day of surgery were excluded. Although 18 patients had previously undergone distal foot-level amputations (e.g., transmetatarsal) and 4 had debridement within the same treatment episode, all of these patients ultimately underwent BKA and were therefore retained in the analysis, indexed at BKA. Finally, 130 patients who underwent non-traumatic BKA were enrolled in this study. There were 117 and 13 patients in the non-AKA and AKA groups, respectively (Fig. 1).
Fig. 1. Flowchart of the study population. BKA: below-knee amputation, YWMC: Yonsei University Wonju Medical Center, AKA: above-knee amputation, DNI: delta neutrophil index.
The mean age was not significantly different between the non-AKA and AKA groups (66.28 ± 12.28 years vs. 61.69 ± 14.31 years, p = 0.21). The proportion of men did not differ significantly between the non-AKA and AKA groups (82.1% vs. 76.9%, p = 0.707). Moreover, no differences were observed in smoking status (p = 0.338) or alcohol consumption (p = 0.216) between the groups. The incidence of comorbidities, such as hypertension, DM, chronic kidney disease, liver cirrhosis, or PAOD, was also not significantly different between the groups (all p > 0.05). The preoperative WBC count, Hb, AST, ALT, serum creatinine, serum albumin, and CRP levels, and DNI did not differ significantly between the groups (p > 0.05) (Table 1).
Table 1. Baseline Characteristics of Patients Who Underwent Non-traumatic Below-Knee Amputation.
| Characteristics | Total (n = 130) | Non-AKA (n = 117) | AKA (n = 13) | p-value | |
|---|---|---|---|---|---|
| Age (yr) | 65.82 ± 12.51 | 66.28 ± 12.28 | 61.69 ± 14.31 | 0.211 | |
| < 65 | 61 | 53 | 8 | 0.266 | |
| ≥ 65 | 69 | 64 | 5 | ||
| Sex (male) | 106 (81.5) | 96 (82.1) | 10 (76.9) | 0.707* | |
| Smoking | 0.338* | ||||
| Non-smoker | 77 (59.2) | 69 (59.0) | 8 (61.5) | ||
| Ex-smoker | 17 (13.1) | 17 (14.5) | 0 | ||
| Current-smoker | 36 (27.7) | 31 (26.5) | 5 (38.5) | ||
| Alcohol consumption | 0.216 | ||||
| Heavy drinker | 27 (20.9) | 26 (22.4) | 1 (7.7) | ||
| Non-heavy drinker | 102 (79.1) | 90 (77.6) | 12 (92.3) | ||
| Comorbidity | |||||
| HTN | 84 (64.6) | 77 (65.8) | 7 (53.9) | 0.542* | |
| DM | 96 (73.9) | 88 (75.2) | 8 (61.5) | 0.323* | |
| CKD | 29 (22.3) | 25 (21.4) | 4 (30.8) | 0.485* | |
| LC | 8 (6.2) | 6 (5.1) | 2 (15.4) | 0.183* | |
| PAOD | 42 (32.3) | 36 (30.8) | 6 (46.2) | 0.348* | |
| Preoperative lab | |||||
| WBC | 10.66 (7.80–14.95) | 10.87 (7.51–15.89) | 9.95 (7.95–14.61) | 0.933 | |
| Hb | 9.8 (8.9–10.8) | 9.8 (8.9–10.9) | 9.4 (8.3–10.7) | 0.591 | |
| AST | 26 (18–45) | 26 (18–46) | 34 (23–37) | 0.367 | |
| ALT | 19 (11–30) | 19 (11–30) | 20 (8–28) | 0.878 | |
| Cr | 1.04 (0.66–2.02) | 1.10 (0.67–2.07) | 0.83 (0.58–1.25) | 0.327 | |
| Albumin | 2.89 ± 0.60 | 2.89 ± 0.61 | 2.86 ± 0.55 | 0.839 | |
| CRP | 7.40 (3.96–13.18) | 7.35 (3.90–14.05) | 9.59 (4.01–12.90) | 0.702 | |
| DNI | 0.9 (0–2.4) | 0.8 (0–2.2) | 1.6 (0–3.2) | 0.281 | |
Values are presented as mean ± standard deviation, number (%), or median (interquartile range).
AKA: above-knee amputation, HTN: hypertension, DM: diabetes mellitus, CKD: chronic kidney disease, LC: liver cirrhosis, PAOD: peripheral arterio-occlusive disease, WBC: white blood cell, Hb: hemoglobin, AST: aspartate transaminase, ALT: alanine aminotransferase, Cr: serum creatinine, CRP: C-reactive protein, DNI: delta neutrophil index.
*Fisher’s exact test showing differences between the non-AKA and AKA groups.
Laboratory Findings on the Day of Surgery
No significant difference in the WBC count was observed between the non-AKA and AKA groups on POD 0, 1, or 6 (all p > 0.05). Similarly, the Hb levels on PODs 0, 1, and 6 were not significantly different between the 2 groups (all p > 0.05). However, the DNI was significantly higher in the AKA group than in the non-AKA group on POD 1 (p = 0.022), whereas no significant difference was observed in the DNI between the non-AKA and AKA groups on POD 0 (p = 0.220) and POD 6 (p = 0.135) (Table 2).
Table 2. Comparison of Postoperative Serial Laboratory Blood-based Markers between Participants in the AKA and Non-AKA Group.
| Outcome | Non-AKA (n=136) | AKA (n=17) | p-value | |
|---|---|---|---|---|
| WBC | ||||
| POD 0 | 11.19 (8.04–16.15) | 10.34 (6.10–15.36) | 0.504 | |
| POD 1 | 12.34 (9.11–15.24) | 11.03 (8.61–12.16) | 0.156 | |
| POD 6 | 8.75 (6.71–11.94) | 12.25 (9.02–12.79) | 0.195 | |
| Hb | ||||
| POD 0 | 9.82 ± 1.53 | 9.96 ± 2.04 | 0.609 | |
| POD 1 | 9.70 ± 1.38 | 9.67 ± 1.19 | 0.475 | |
| POD 6 | 9.70 ± 1.20 | 10.13 ± 1.06 | 0.727 | |
| DNI | ||||
| POD 0 | 0.8 (0–2.2) | 1.5 (0.3–3.3) | 0.220 | |
| POD 1 | 1.0 (0–2.3) | 2.3 (1.3–4.1) | 0.022 | |
| POD 6 | 0.6 (0–1.7) | 1.4 (0–3.2) | 0.135 | |
Values are presented as median (interquartile range) or mean ± standard deviation.
AKA: above-knee amputation, WBC: white blood cell, POD: postoperative day, Hb: hemoglobin, DNI: delta neutrophil index.
Odds Ratio of the DNI for Predicting AKA within 30 days in Patients Undergoing Non-traumatic BKA
Since the DNI on POD 1 was found to be significantly different in the non-AKA and AKA groups, we investigated whether it was a prognostic factor for early AKA. The odds ratio (OR) for early AKA according to the DNI on POD 1 in patients undergoing non-traumatic BKA was 1.46 (95% CI, 1.03–2.08), accounting for age, sex, alcohol consumption, and smoking. When the patients were classified according to age, the OR for early AKA according to the DNI on POD 1 in patients undergoing non-traumatic BKA aged < 65 years and ≥ 65 years was 1.62 (95% CI, 1.06–2.47) and 1.02 (95% CI, 0.43–2.40), respectively (Table 3).
Table 3. Odds Ratio of 30-Day Above-Knee Amputation with Postoperative Day 1 DNI in Patients Who Underwent Non-traumatic Below-Knee Amputation.
| n | OR (95% CI) | p-value | ||
|---|---|---|---|---|
| Total | 130 | |||
| Crude | 1.46 (1.08–1.97) | 0.014* | ||
| Model 1 | 1.41 (1.02–1.96) | 0.041* | ||
| Model 2 | 1.46 (1.03–2.07) | 0.034* | ||
| Age < 65 yr | 61 | |||
| Crude | 1.56 (1.07–2.27) | 0.020* | ||
| Model 1 | 1.56 (1.07–2.27) | 0.022* | ||
| Model 2 | 1.62 (1.06–2.47) | 0.025* | ||
| Age ≥ 65 yr | 69 | |||
| Crude | 1.06 (0.49–2.29) | 0.886 | ||
| Model 1 | 1.11 (0.53–2.29) | 0.788 | ||
| Model 2 | 1.02 (0.43–2.40) | 0.971 | ||
Model 1: adjusted for age and sex, Model 2: adjusted for age, sex, alcohol consumption, and smoking.
DNI: delta neutrophil index, OR: odds ratio.
*Statistically significant at p < 0.05.
ROC Curve Analysis of the Biomarkers Predicting AKA within 30 Days in Patients Undergoing Non-traumatic BKA
The AUROC of the DNI on POD 1, WBC count, and Hb level for predicting early AKA in patients undergoing non-traumatic BKA was 0.700 (95% CI, 0.534–0.866), 0.335 (95% CI, 0.167–0.503), and 0.537 (95% CI, 0.348–0.727), respectively. The optimal cutoff value of the DNI on POD 1 was 1.95, with a sensitivity and specificity of 0.73 and 0.69, respectively (Fig. 2). Moreover, the AUROC of the DNI on POD 1 for predicting early AKA in patients aged < 65 years and ≥ 65 years was 0.770 (95% CI, 0.574–0.967) and 0.589 (95% CI, 0.306–0.872), respectively (p = 0.302) (Fig. 3). The AUROCs of the preoperative CRP, serum creatinine, serum albumin, AST, and ALT levels were 0.539 (95% CI, 0.347–0.730), 0.586 (95% CI, 0.411–0.761), 0.508 (95% CI, 0.329–0.688), 0.413 (95% CI, 0.257–0.570), and 0.510 (95% CI, 0.331–0.690), respectively (Fig. 4).
Fig. 2. Receiver operating characteristic curve analysis regarding the postoperative day 1 biomarkers as predictive factors for 30-day above-knee amputation in patients undergoing non-traumatic below-knee amputation. The diagonal line indicates the no-discrimination reference (area under the receiver operating characteristic curve [AUROC], 0.5). DNI: delta neutrophil index, WBC: white blood cell, Hb: hemoglobin.
Fig. 3. Receiver operating characteristic curve analysis of postoperative day 1 biomarkers as predictive factors for 30-day above-knee amputation in patients undergoing non-traumatic below-knee amputation according to age (< 65 years vs. ≥ 65 years). The diagonal line indicates the nodiscrimination reference (area under the receiver operating characteristic curve [AUROC], 0.5).
Fig. 4. Receiver operating characteristic curve analysis of preoperative biomarkers as predictive factors for 30-day above-knee amputation in patients undergoing non-traumatic below-knee amputation. The diagonal line indicates the no-discrimination reference (area under the receiver operating characteristic curve [AUROC], 0.5). CRP: C-reactive protein, Cr: serum creatinine, AST: aspartate transaminase, ALT: alanine aminotransferase.
DISCUSSION
The DNI is a useful diagnostic marker of infection and sepsis.14,16) Since it can be calculated automatically using a specific type of blood-cell analyzer when conducting complete blood cell analysis, determining the DNI is convenient, repeatable, and cost-effective. Moreover, previous studies have demonstrated the efficacy of the DNI as a prognostic marker for complications after surgery, such as kidney transplantation22,23) and esophagectomy.24)
To the best of our knowledge, this is the first study to investigate the prognostic value of the DNI in patients undergoing non-traumatic BKA. From these results, a 1-unit increase in the DNI was associated with a significantly increased risk of ipsilateral AKA within 30 days (OR, 1.46; 95% CI, 1.03–2.08). It was also observed that the DNI had an acceptable predictive value for early ipsilateral AKA (AUROC, 0.700; 95% CI, 0.534–0.866). Therefore, the POD 1 DNI can be a potential biomarker to predict early ipsilateral AKA in non-traumatic BKA patients.
Previous studies have routinely investigated blood parameters for predicting re-amputation in patients with DM and/or PAOD.2,12,19) Czerniecki et al.2) reported that a WBC count ≥ 11,000/µL was associated with an increased risk of re-amputation within 1 year in patients with DM and/or PAOD (coefficient = +0.583). Norvell and Czerniecki12) reported that a WBC count ≥ 11,000/µL was associated with a significantly increased risk of re-amputation within 1 year in patients with DM and/or PAOD (adjusted hazard ratio, 1.7; 95% CI, 1.5–1.8). However, the present study results revealed that the DNI on POD 1 (0.700; 95% CI, 0.534–0.866) had a higher predictive value for the 30-day revisional AKA compared to the WBC count on POD 1 (AUROC, 0.335; 95% CI, 0.167–0.503) in patients with DM and/or PAOD (p < 0.001) (Fig. 2). This suggests that the DNI is a potentially useful biomarker for predicting re-amputation in patients with BKA.
Gülcü et al.19) identified 3 preoperative routine blood parameters with the highest predictive value for re-amputation in patients with diabetic foot: glycated Hb (AUROC, 0.785; 95% CI, 0.728–0.842), CRP (AUROC, 0.627; 95% CI, 0.550–0.704), and serum creatinine (AUROC, 0.690; 95% CI, 0.609–0.770). In our study, the AUROC of the DNI on POD 1 was higher than those of preoperative CRP (AUROC, 0.539; 95% CI, 0.347–0.730) and serum creatinine (AUROC, 0.586; 95% CI, 0.411–0.761) (Fig. 4), consistent with the preoperative timing in Gülcü et al.19) Further, unlike previous studies,25) the DNI was used on POD 1, WBC count, and Hb level to predict outcomes in patients undergoing non-traumatic BKA to represent their conditions after surgery. Potential predictive markers, such as glycated Hb on POD 1 and CRP on POD 1, were not investigated because the levels of these markers were not determined on the day after amputation.
CBC is a routine, low-cost test obtained pre- and postoperatively in most surgical pathways to assess hematologic status (e.g., anemia, leukocytosis, thrombocytopenia).26) In contrast, inflammatory markers such as CRP are typically ordered selectively when infection or inflammation is clinically suspected and are not obtained as consistently as CBC.27) Concurrently, while recent initiatives have encouraged reducing non-essential perioperative testing,28) clear guidance on when to add postoperative inflammatory panels is unavailable. In this context, these findings support POD 1 DNI—derived from the routine CBC—as a cost-effective, first-line screen after BKA: an elevated DNI can flag patients for additional inflammatory testing (e.g., CRP, procalcitonin) when indicated and assist in early risk stratification for proximal conversion, while not serving as a stand-alone trigger for pre-emptive AKA. Prospective studies are warranted to validate thresholds and to formalize a pragmatic, stepwise testing algorithm.
This study had some limitations. First, although all patients ultimately underwent BKA, the level of their initial amputation was not analyzed (e.g., transmetatarsal or Syme) within the same treatment episode,2,12) including other factors such as glycemic control,19,25) abnormal ankle-brachial index,12) angioplasty status, and anticoagulant or aspirin use,9) which are associated with the risk of complications in patients undergoing BKA, and this may represent a potential limitation in drawing valid conclusions from our results. Furthermore, subgroup analyses according to sex and indication (DM, PAOD, and DM + PAOD) were not performed due to a small sample size. However, prior studies suggest a higher risk of amputation in male patients29) and those with concurrent DM and PAOD;30) larger studies are needed to confirm these findings. Second, during the study period, major amputations (BKA/AKA) predominated at our center, limiting direct comparisons across a broad spectrum of amputation levels. Moreover, postoperative CRP was not obtained routinely and was available in very few patients, precluding a reliable head-to-head comparison with POD 1 DNI. Third, perioperative factors, including inflammatory burden from preceding distal procedures, intraoperative blood loss, and systemic inflammatory responses, were not standardized or consistently captured, which may influence POD 1 DNI; therefore, the ≈1.95 threshold should be interpreted as cohort-specific rather than a universal decision rule. Fourth, since this study was conducted in a hospital-based setting, patient characteristics may be more severe than those in population-based settings. However, the cumulative incidence of the 30-day ipsilateral re-amputation in this study was 10%, which is similar to that in the Danish Amputation Register study.11) Finally, the AUROC of POD 1 DNI as a predictive factor for ipsilateral AKA within 30 days in patients aged ≥ 65 years was 0.589, suggesting limited prognostic utility in older patients.
In conclusion, among patients aged < 65 years undergoing BKA, POD 1 DNI showed better prognostic performance than the postoperative WBC count for predicting ipsilateral AKA within 30 days. Since DNI is obtained from a routine, low-cost CBC test, a high POD 1 DNI can be used (1) as a first-line screening tool before ordering additional inflammatory tests and (2) as an adjunctive prognostic indicator of early proximal conversion—rather than a mandate for preemptive AKA. Prospective studies with routine postoperative inflammatory panels are needed to validate cutoffs and clinical pathways.
ACKNOWLEDGEMENTS
This research was supported by grants from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: HI23C0476); the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) (No. RS-2023-00251307); the Ministry of Trade, Industry and Energy, Korea, under the “Regional Innovation Cluster Development Program (R&D, P0025898)” supervised by the Korea Institute for Advancement of Technology (KIAT); and a grant of the medical data-driven hospital support project through the Korea Health Information Service (KHIS), funded by the Ministry of Health & Welfare, Republic of Korea.
Footnotes
CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported.
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