Dear Editor, I read this manuscript with considerable interest. The study examines the economic differences between percutaneous transforaminal endoscopic discectomy (PTED) and unilateral biportal endoscopy (UBE) for lumbar disc herniation (LDH) within the context of diagnosis-related group (DRG) payment reform1. While the topic occupies an important intersection of clinical decision-making and health-economic policy, several methodological and interpretive limitations raise concerns about the robustness of the conclusions and their policy implications. Within the framework of the TITAN Guidelines, this letter therefore respectfully offers several points for further consideration2. First, although the authors aim to evaluate cost differences “within the DRG payment framework,” their analysis relies entirely on fee-for-service itemized charges rather than DRG-based reimbursement data. Under DRG payment, the amount paid per case is determined by the grouping rules and group weight (Payment = Base Rate × Weight), independent of a hospital’s actual itemized charges. Without examining how PTED and UBE cases were grouped, the DRG settlement results, outlier handling, or weight consumption, the conclusion that PTED has a financial “advantage” lacks grounding in true DRG mechanisms. Lower charges do not necessarily translate into financial benefit for hospitals or payers under DRG. Second, case complexity is central to DRG grouping and expected cost, yet the study does not include key clinical indicators such as the degree of stenosis, canal morphology, disc migration, or neurological deficits. Without proper complexity adjustment, PTED cases – which typically involve less severe pathology – will naturally appear less costly than UBE. This represents a classic case-mix bias. Within DRGs, such bias distorts grouping decisions and weight assignment, rendering the economic comparison unsuitable for informing policy. Third, the authors interpret lower PTED charges as evidence of its “advantage” under DRG, which reflects a misunderstanding of DRG incentives. DRGs do not reward the cheapest operation; they reward appropriate, standardized, value-based care that fits the expected resource profile of each group. If UBE is more appropriate for complex stenosis, choosing PTED merely because it appears cheaper undermines the principle that clinical appropriateness takes precedence over nominal cost under DRG. Fourth, although the manuscript states repeatedly that PTED and UBE yield “similar clinical outcomes,” it is well recognized that UBE is often preferred for severe central stenosis or anatomically complex cases. The study acknowledges this only briefly and still does not stratify patients by complexity3. Without clearly distinguishing indications, PTED’s lower cost may simply reflect treatment of less challenging cases rather than genuine economic efficiency. The subgroup analysis of stenosis is insufficient to capture disease-severity heterogeneity; meaningful comparison requires finer stratification (e.g., mild/moderate/severe stenosis; presence of lateral recess stenosis). The discussion extrapolates the findings to support broader DRG reform recommendations, yet the analysis never incorporates actual DRG grouping logic, weight coefficients, reimbursement rules, or real settlement data. Thus, policy-oriented claims – particularly that PTED is more “sustainable” under DRG – lack empirical foundation. DRG payments are not based on itemized charges but on standardized payment for disease severity and resource use. Without assessing how PTED and UBE would be grouped and whether fixed DRG payments align with actual expenditure, such policy arguments remain speculative. Fifth, the study focuses on 3-month recurrence rates, reoperation rates, and VAS pain scores, which is insufficient for evaluating spine surgery outcomes4,5. Differences in decompression adequacy between UBE and PTED may have important long-term implications for symptom relief and recurrence. Without longer-term outcomes such as ODI, quality of life, or return-to-work data, drawing cost-effectiveness conclusions risks premature or misleading interpretation. Moreover, costs such as anesthesia and consumables are heavily influenced by institutional pricing and procurement policies rather than surgical technique. Presenting these differences as inherent to PTED or UBE is therefore problematic. The lack of multicenter data and price-variation sensitivity analyses limits the generalizability of the economic conclusions. Lastly, although the use of LASSO and elastic-net models is methodologically reasonable for variable selection and overfitting control, the predictors identified – such as sex and total length of stay – do not reflect the core determinants of DRG grouping. DRGs are fundamentally organized around “diagnosis + severity,” not administrative or demographic variables. The failure to identify essential grouping factors (principal diagnosis, CC/MCC, severity levels) indicates that the model diverges from actual DRG operation. The modest explanatory power (R2 ≈ 0.44) further suggests that more than half of cost variability is driven by unmeasured clinical complexity, disease severity, and resource intensity – all central to DRG design. For DRG-related policy research, such limitations undermine both predictive utility and relevance to payment-model evaluation. In summary, while the study provides descriptive insights into the itemized cost structure of PTED and UBE, it does not accurately reflect DRG payment behavior, grouping logic, or whole-cycle economic impact. As clinicians directly involved in DRG implementation, we must emphasize that analyses lacking proper methodological foundation should not guide DRG-related decision-making, care-pathway design, or clinical policy preferences. Economic evaluations aligned with DRG principles require standardized grouping rules, complexity adjustment, multicenter cost data, and long-term outcome assessment. I encourage the authors to address these gaps before deriving policy-level conclusions.
Ji et al. (Wed,) studied this question.