Accurate pain assessment is essential for effective pain management. However, due to the complex and subjective nature of pain, objective assessment in clinical practice remains challenging. Widely used pain assessment scales, such as the numeric rating scale (NRS) and visual analog scale (VAS), commonly applied in postoperative pain evaluation, have considerable limitations [1]. These scales provide a simple rating system; however, they lack specific guidance beyond the extremes of their range, thus requiring patients to interpret their pain and translate it to numerical values. This process can be particularly challenging for individuals with diminished cognitive function. The subjective nature of these scales leads to considerable variability in pain reporting among individuals, as no standardized reference point exists [2]. Furthermore, these tools focus exclusively on pain intensity, neglecting other important dimensions including functional impairment and emotional distress [3], resulting in incomplete assessment of pain experience and suboptimal treatment decisions.

To address these limitations, alternative pain assessment tools have been developed. One such tool is the defense and veterans pain rating scale (DVPRS), created by the US Army Surgeon General Pain Management Task Force, specifically for military populations [4,5]. The DVPRS combines the NRS with descriptive words, color coding, and facial expressions, offering a multimodal approach to improve communication and understanding of pain intensity, particularly for individuals who may struggle with traditional rating scales. It also includes supplementary questions addressing the impact of pain on daily activities, sleep, mood, and stress, enabling a more comprehensive assessment of pain experience. Although initially designed for military use, the DVPRS has the potential for assessing pain in other settings, including in surgical patients [1].

However, the Korean version of the DVPRS (K-DVPRS) has not yet been validated, and to the best of the authors’ knowledge, only one study has evaluated its application in acute postoperative pain [6]. The aim of this study was to validate the K-DVPRS and assess its effectiveness in acute postoperative pain management. It was hypothesized that the K-DVPRS would have a significant correlation with the 11-point NRS, a widely used tool for postoperative pain assessment and that pain intensity measured by the K-DVPRS would significantly correlate with early postoperative recovery, as measured by the EuroQol 5-Dimension 5-Level (EQ-5D-5L).

This prospective observational study was approved by the Institutional Review Board of Seoul National University Hospital (approval no. 2311-172-1489, December 13, 2023) and registered at ClinicalTrials.gov (NCT06210802, January 08, 2024). Written informed consent was obtained from all patients before their participation. This study complied with the Strengthening the Reporting of Observational Studies in Epidemiology guidelines [7].

Eligible participants included patients aged 19–70 years scheduled for elective laparoscopic or robotic abdominal surgery lasting over 1 hour under general anesthesia at Seoul National University Hospital. Patients with an American Society of Anesthesiologists (ASA) physical status ≥ III, unable to complete the questionnaire, with red-green color blindness or difficulty distinguishing colors, and those deemed unsuitable by the researcher’s judgment were excluded.

1. Translation and cultural adaption of the DVPRS

The original English version of DVPRS 2.0 was translated into Korean (K-DVPRS) using a forward-backward translation method to minimize any alterations in the original DVPRS content, similar to the approach used in the authors’ previous study on the Korean translation of the quality of recovery 15 questionnaires [8]. Two authors (SC and H-JL) first translated the original DVPRS 2.0 into Korean. Subsequently, a bilingual author (TYK) who had received university education in the United States translated the Korean version back into English. Afterwards, the three authors (SC, TYK, and H-JL) compared the original with the reverse-translated questionnaire and evaluated each item on a 7-point scale (1 = no concordance, 7 = perfect concordance). Items that received a score between 5 and 7 were included in the final version, while those that did not meet the criteria were reviewed. The K-DVPRS used in this study is presented in Appendix 1, 2.

2. Study protocol

To evaluate the preoperative state, the K-DVPRS and K-DVPRS supplemental questions and the EQ-5D-5L questionnaire were administered to patients the day before surgery. At 24 hours postoperatively, pain intensity at rest and during coughing was assessed using the 11-point NRS (0 = no pain, 10 = worst pain imaginable) and K-DVPRS, respectively. The K-DVPRS supplemental questions and EQ-5D-5L questionnaire were also administered. The EQ-5D-5L, a comprehensive questionnaire, evaluates five health-related dimensions including mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, using a five-level scale ranging from "no problems" to "unable to do." It also includes a 0–100 visual analog scale (EQ-VAS) for assessing overall health on the evaluation day [9]. The American Society for Enhanced Recovery and the Perioperative Quality Initiative recommend the EQ-5D-5L as one of the tools for assessing the postoperative recovery quality [10]. In this study, the EQ-5D-5L questionnaire was used in its Korean version with prior authorization from the EuroQol Group (https://euroqol.org). The postoperative order of assessments was NRS, K-DVPRS, K-DVPRS supplemental questions, and EQ-5D-5L questionnaire. To assess the reliability of the K-DVPRS, pain intensity was remeasured using the K-DVRPS 30 minutes later. If rescue analgesics were administered between the initial assessment and reassessment, reassessment was not conducted. At 48 hours postoperatively, pain assessments and questionnaires were administered in the same sequence. If patients had difficulty assessing pain intensity using the NRS and K-DVPRS, additional guidance was provided with explanations consistent with the initial assessment, and the patients were encouraged to carefully review the information provided for the K-DVPRS. If they still could not respond after receiving further instructions, failure to respond was recorded. Furthermore, patients’ sex, age, height, weight, body mass index, ASA physical status, surgery duration, surgery type, and surgery extent (major vs. extra major/complex) were assessed using the Surgical Outcome Risk Tool classification [11]. All assessments and investigations were conducted by a research nurse who was not an author of the study.

3. Sample size calculation

A previous study validating the German DVPRS included 135 patients [6]. Considering an expected 10% dropout rate, 150 patients were included in this study.

4. Statistical analysis

Categorical variables were presented as the number of patients (proportion), while continuous variables were presented as mean (standard deviation) or median (interquartile range), depending on the data distribution. For continuous variables, normality was assessed using the Shapiro–Wilk test.

First, convergent and construct validities were assessed. Convergent validity was evaluated using Spearman’s correlation analyses between pain intensities assessed using the K-DVPRS and NRS at rest and during coughing at 24 and 48 hours postoperatively, respectively [12]. Construct validity was assessed by comparing K-DVPRS pain scores at rest and during coughing at 24 and 48 hours postoperatively across subgroups based on sex, surgery duration (≤ 120 minutes vs. > 120 minutes), and surgery extent (major vs. extra major/complex) using the Mann–Whitney U-test. These factors were selected based on their established effect on postoperative pain intensity [13,14]. Moreover, comparisons of pain scores at rest and during coughing were incorporated during the revision process and analyzed using Wilcoxon signed-rank tests at 24 and 48 hours postoperatively to further evaluate construct validity. Bland–Altman analyses were conducted to assess the agreement between the NRS and K-DVPRS, as high correlation alone does not guarantee interchangeability between the two scales. The mean differences and limits of agreement (LOA, mean difference ± 1.96 standard deviations) were calculated to quantify the interchangeability level between the scales [15].

Second, the K-DVPRS reliability was evaluated through internal consistency and test-retest reliability. Internal consistency was assessed by calculating Cronbach’s alpha coefficient for the four K-DVPRS supplemental questions, and the pain intensity scores at rest and during coughing were measured at 24 and 48 hours postoperatively. Test-retest reliability was assessed using the intraclass correlation coefficient (ICC) by evaluating the pain intensity scores at rest and during coughing at 24 hours postoperatively and 30 minutes apart.

Third, the K-DVPRS responsiveness was evaluated using Cliff’s delta effect size due to the non-normal distribution of pain scores. Cliff’s delta values of 0.15–0.33, 0.33–0.47, and ≥ 0.47 were interpreted as small, medium, and large effect sizes, respectively. Responsiveness was calculated separately for pain intensity at rest and during coughing, comparing changes from preoperative to 24 hours postoperatively and from 24 to 48 hours postoperatively.

Finally, the correlation between postoperative pain severity, measured by NRS and K-DVPRS, early postoperative recovery, evaluated using the EQ-visual analog scale (EQ-VAS), and EQ-5D-5L index scores weighted for the Korean population was analyzed using Spearman’s correlation analyses [16]. Differences in correlation coefficients were evaluated using the Steiger Z-test [17].

All statistical analyses were performed using R version 4.4.1 (R Foundation for Statistical Computing). A P value of < 0.05 was considered statistically significant.

Overall, 174 patients were screened with 8 excluded based on the exclusion criteria and 16 declining consent, resulting in 150 enrolled participants. Of these, two patients were excluded after surgery (one withdrew consent to participate and one converted to open surgery), resulting in 148 patients for data analysis (Fig. 1). At 48 hours postoperatively, 145 patients were included in the analysis, as 3 were discharged earlier and could not complete the survey. Demographic and surgery-related variables are presented in Table 1.

Table 1 Baseline characteristics

Variables	Value (n = 148)
Female	77 (52.0)
Age (yr)	59 (49–65)
ASA physical status
I	41 (27.7)
II	107 (72.3)
Preoperative EQ-VAS	90.0 (80.0–95.0)
Preoperative EQ-5D-5L indexa	1.00 (0.87–1.00)
Surgical extentb
Major	60 (40.5)
Extra major/complex	88 (59.5)
Type of surgery
General surgery	57 (38.5)
Gynecological surgery	30 (20.3)
Urological surgery	61 (41.2)
Duration of surgery (min)	115 (80–175)

Values are presented as number (%) or median (interquartile range).

ASA: American Society of Anesthesiologists, EQ-VAS: EuroQoL visual analogue scale, EQ-5D-5L: EuroQol 5-dimensional 5-level.

^aEuroQol 5-dimensional 5-level index scores were calculated using the weights reported in a previous study conducted in the Korean population. ^bThe extent of surgery was classified according to the Surgical Outcome Risk Tool classification.

Figure 1. Flow chart of the study.

Both the NRS and K-DVPRS had 100% completion rates on postoperative days one and two. At 24 hours postoperatively, the correlation between K-DVPRS and NRS was strong, with a Spearman's ρ of 0.78 (95% confidence interval [CI]: 0.70–0.84, P < 0.001) at rest and 0.77 (95% CI: 0.68–0.84, P < 0.001) during coughing. Similarly, at 48 hours postoperatively, the correlation remained robust, with ρ values of 0.75 (95% CI: 0.64–0.84, P < 0.001) at rest and 0.75 (95% CI: 0.67–0.83, P < 0.001) during coughing. Construct validity was supported by significant differences in pain scores based on surgical extent and duration (Table 2). Both K-DVPRS and NRS detected significant differences based on surgical extent at 24 hours during coughing and 48 hours at rest and during coughing, with additional differences at 48 hours during coughing based on surgical duration. Wilcoxon signed-rank test also confirmed significant differences between pain at rest and during coughing (all P < 0.001), further validating the K-DVPRS.

Table 2 Pain intensity assessed by the K-DVPRS according to sex, duration of surgery, and extent of surgery at 24 and 48 hr postoperatively

	K-DVPRS at rest		P valuea.,b	K-DVPRS during coughing		P valuea.,b
At 24 hr postoperatively
Sex	Male	Female		Male	Female
	3.0 (1.0–4.0)	3.0 (1.0–4.0)	0.720	7.0 (6.0–8.0)	6.0 (5.0–8.0)	0.331
Duration of surgery	≤ 120 min	> 120 min		≤ 120 min	> 120 min
	2.0 (1.0–4.0)	3.0 (1.0–4.0)	0.386	6.0 (5.0–8.0)	7.0 (6.0–8.0)	0.087
Extent of surgery	Major	Extra major/complex		Major	Extra major/complex
	2.0 (1.0–3.0)	3.0 (2.0–4.0)	0.057	5.0 (4.0–8.0)	8.0 (6.0–8.0)	< 0.001
Total	3.0 (1.0–4.0)			7.0 (5.0–8.0)		< 0.001
At 48 hr postoperatively
Sex	Male	Female		Male	Female
	2.0 (1.0–3.0)	2.0 (1.0–3.3)	0.903	6.0 (4.0–8.0)	6.0 (4.0–7.0)	0.495
Duration of surgery	≤ 120 min	> 120 min		≤ 120 min	> 120 min
	2.0 (1.0–3.0)	2.0 (1.0–4.3)	0.051	5.0 (3.8–7.0)	6.0 (5.0–8.0)	0.004
Extent of surgery	Major	Extra major/complex		Major	Extra major/complex
	2.0 (1.0–3.0)	2.0 (1.0–4.0)	0.136	5.0 (3.0–7.0)	6.0 (5.0–8.0)	0.006
Total	2.0 (1.0–3.0)			6.0 (4.0–7.0)		< 0.001

Values are presented as median (interquartile range).

K-DVPRS: Korean version of defense and veterans pain rating scale.

^aP values compare male versus female, duration of surgery ≤ 120 min versus > 120 min, major versus extra major/complex extent of surgery, and pain at rest versus during coughing. ^bPain intensity was compared by sex, surgery duration, and extent of surgery using the Mann–Whitney U-test, while pain intensity at was compared with that while coughing using the Wilcoxon signed-rank test.

The results of the Bland–Altman analyses are presented in Supplementary Fig. 1. The LOA was as follows: pain at rest at 24 hours postoperatively (–2.29 to 3.12), pain during coughing at 24 hours postoperatively (–3.06 to 2.71), pain at rest at 48 hours postoperatively (–2.74 to 2.93), and pain during coughing at 48 hours postoperatively (–2.87 to 3.07). The broad LOAs between the two measures indicated that they are not interchangeable.

The internal K-DVPRS consistency was acceptable with a Cronbach’s alpha coefficient of 0.77 (95% CI: 0.71–0.83) at 24 hours postoperatively and 0.85 (95% CI: 0.81–0.89) at 48 hours postoperatively. The test-retest reliability of the 24 hours postoperative assessment was excellent with an ICC of 0.90 (95% CI: 0.86–0.93) for pain score at rest and 0.95 (95% CI: 0.93–0.96) during coughing.

Cliff’s effect size for pain scores from the preoperative day to 24 hours postoperatively was –0.88 (95% CI: –0.94 to –0.77) at rest and –1.00 (95% CI: –1.00 to –0.99) during coughing indicating high K-DVPRS responsiveness. From 24 to 48 hours postoperatively, Cliff’s effect size was 0.14 (95% CI: 0.11–0.27) at rest and 0.29 (95% CI: 0.16–0.41) during coughing. Detailed results of the responsiveness of the K-DVPRS, NRS, EQ-VAS, and EQ-5D-5L indices are presented in Supplementary Table 1.

The correlations between the K-DVPRS, NRS, EQ-VAS, and EQ-5D-5L indices at 24 and 48 hours postoperatively are presented in Figs. 2, 3, respectively. At 24 hours postoperatively, no significant differences were observed in the correlation coefficients between pain intensity measured by the NRS and K-DVPRS, both at rest and during coughing, with the EQ-VAS and EQ-5D-5L indices. However, at 48 hours postoperatively, pain intensity at rest assessed by K-DVPRS had a stronger correlation with the EQ-5D-5L index (ρ = –0.55 versus ρ = –0.41, P = 0.006) and EQ-VAS (ρ = –0.36 versus ρ = –0.24, P = 0.033) than that assessed by NRS. Similarly, pain intensity during coughing measured by K-DVPRS had a stronger correlation with EQ-VAS compared to the NRS (ρ = –0.41 versus ρ = –0.26, P = 0.007). The comparison of correlation coefficients between the two pain scales and postoperative recovery, as assessed by the EQ-5D-5L index and EQ-VAS, is presented in Supplementary Table 2.

Figure 2. Correlations between the K-DVPRS, NRS, EQ-VAS, and EQ-5D-5L index at 24 hr postoperatively. K-DVPRS: Korean version of defense and veterans pain rating scale, NRS: numeric rating scale, EQ-VAS: EuroQoL visual analogue scale, EQ-5D-5L: EuroQol 5-dimensional 5-level. **P < 0.01, ***P < 0.001.

Figure 3. Correlations between the K-DVPRS, NRS, EQ-VAS, and EQ-5D-5L index at 48 hr postoperatively. K-DVPRS: Korean version of defense and veterans pain rating scale, NRS: numeric rating scale, EQ-VAS: EuroQoL visual analogue scale, EQ-5D-5L: EuroQol 5-dimensional 5-level. **P < 0.01, ***P < 0.001.

The correlations between pain scores at rest and during coughing at 24 and 48 hours postoperatively, assessed using the K-DVPRS or NRS, and K-DVPRS supplemental questions are presented in Supplementary Figs. 2, 3.

This study validated the K-DVPRS for assessing acute postoperative pain in Korean patients undergoing surgery. The K-DVPRS had strong convergent validity with the 11-point NRS, good internal consistency, excellent test-retest reliability, and high responsiveness to changes in pain levels. Construct validity was confirmed by significant differences in pain intensity based on surgery duration and extent. Furthermore, pain intensity measured by the K-DVPRS had a stronger correlation with early postoperative recovery, as assessed by the EQ-5D-5L, than with the NRS. These findings suggest that K-DVPRS is a valuable tool for evaluating postoperative pain.

Despite its potential, the DVPRS has not been widely used in perioperative settings. A recent study explored the association between the DVPRS, NRS, and the PROMIS short form in patients who underwent extremity fracture surgery [18]. However, this study was limited to outpatient assessments conducted two weeks postoperatively, which differs from this study’s focus on acute postoperative pain. A French DVPRS validation study included patients undergoing surgery but did not specifically target postoperative pain [19]. Another study validated a modified DVPRS for patients undergoing total joint replacement with similar responsiveness to the Short-Form McGill Pain Questionnaire with less respondent burden [6]. Unlike previous studies, this study specifically addressed acute postoperative pain and compared the K-DVPRS with the commonly used NRS. The association between pain intensity measured using the K-DVPRS and early postoperative recovery was also investigated.

Although both the K-DVPRS and NRS use a 0–10 scale and had a strong correlation in this study, the LOA between these two measures was broad, indicating they were not interchangeable. This discrepancy likely arises from the distinct information provided by each scale. The NRS is relatively abstract, offering only extreme pain descriptors without defining intermediate values. This lack of detail has led some studies to question its accuracy and reliability as a pain assessment tool. Several studies have reported that pain intensity assessed by the NRS does not adequately reflect pain tolerability, clinically significant pain, or the desire for additional opioid administration [3,20–22]. This is likely due to the lack of definition between its two extremes, allowing considerable subjective interpretation by patients. Furthermore, such subjective assessments may pose challenges to healthcare providers when interpreting patients’ pain [23]. While, the DVPRS includes specific descriptors, colors, and facial expressions for each score, providing a more concrete representation of pain levels and potentially enhancing accuracy. In the emergency department setting, the DVPRS has been suggested to better differentiate between moderate and severe pain compared to the NRS [24], which may assist in making appropriate decisions regarding analgesic administration [25]. This study revealed that the K-DVPRS had a stronger correlation with early postoperative recovery at 48 hours, as measured by the EQ-VAS and EQ-5D-5L index than the NRS, suggesting that the K-DVPRS may better capture the postoperative pain experience. Therefore, the K-DVPRS provides more precise insights into pain, enabling the development of more effective pain management strategies. These strategies reduce the unnecessary use of analgesics, including opioids, and address the risk of inadequate treatment from pain underestimation, ensuring appropriate and comprehensive patient care.

The DVPRS supplemental questions offer a broader evaluation of how pain affects postoperative recovery in terms of activities, sleep, mood, and stress, which are significantly impacted by postoperative pain [26,27]. This multifaceted assessment of postoperative pain better captures pain’s impact on postoperative recovery. However, unidimensional scales like the NRS may not completely capture the complexity of the pain, as they focus solely on pain intensity and overlook its multifaceted nature, encompassing emotional, psychological, and contextual factors. Furthermore, because a unidimensional pain scale, like the NRS, may be more influenced by emotional aspects than sensory aspects of pain [28], failing to simultaneously evaluate the impact of pain on mood or stress could result in an incomplete and less accurate patient pain assessment. Identification of various factors affected by pain through the K-DVPRS, can facilitate tailor-made interventions for personalized and effective postoperative care, enhancing the patient’s postoperative recovery. For instance, if postoperative pain significantly disrupts sleep, improving night-time pain control along with sleep-promoting pharmacological agents may be beneficial [29]. Similarly, if pain affects mood, psychological interventions can support managing the emotional effects of pain [30]. Thus, by incorporating the DVPRS into postoperative pain management, healthcare providers can refine their strategies and improve overall patient outcomes.

This study provides valuable insights; however, it had several limitations. First, the sample was limited to cognitively intact patients aged < 70 years who were unlikely to face difficulties with the numeric pain scale. This restriction may have prevented the authors from fully exploring the potentially higher response rate of the DVPRS among older adults, particularly those with cognitive impairment. These populations may face more challenges with traditional numeric scales, making them essential for evaluating the DVPRS's applicability and advantages. Future studies should assess its performance and practicality in these groups to explore its potential in diverse settings. Second, as the NRS was used as a comparator for the K-DVPRS validation, the inherent limitations of the NRS are worthy of note, including its subjective nature. Third, this study did not explore patient preferences between the two pain scales. According to one study, some participants found various elements of the DVPRS beneficial; however, others were confused by its excessive information [31]. The preferences for these scales may vary among patients. Fourth, the preoperative K-DVPRS use to assess patients' baseline status may have affected their postoperative responses. While preoperative education on pain assessment tools is generally recommended, it has not been widely implemented in many settings. Consequently, if patients encounter the K-DVPRS for the first time postoperatively, their responses and outcomes may differ from those observed in this study. Fifth, the order in which the pain scales were administered may have influenced the results, as completing one scale could affect responses on the other. The NRS was administered before the K-DVPRS due to its more detailed nature; however, reversing this order may have yielded different outcomes. Sixth, although no definitive guidelines regarding the optimal sample size for validating pain scales have been established, it must be acknowledged that larger sample sizes, as included in other studies validating the DVPRS [5,32], could further strengthen the generalizability of this study’s findings. Finally, the authors were unable to apply the K-DVPRS to patients immediately after surgery, highlighting a potential limitation of the DVPRS in early postoperative pain assessment. Some DVPRS pain intensity descriptors including references to "usual" or "daily activities," are not suitable for patients in the immediate postoperative period. Moreover, the supplemental questions in the DVPRS focus on the impact of pain over the past 24 hours, prompting assessments at 24 and 48 hours postoperatively. These factors indicate that the DVPRS may have limitations in representing pain during the most acute postoperative phase with pain typically at its peak.

This study provided strong evidence supporting the validity, reliability, and responsiveness of the K-DVPRS for assessing acute postoperative pain. The comprehensive nature of the DVRPS, including its supplemental questions, may facilitate more accurate evaluation of pain intensity as compared to the NRS, while also considering its impact on postoperative recovery. The K-DVPRS has the potential for assessing pain in surgical patients and could contribute to improved postoperative care. Future research should explore the DVPRS in different languages and among diverse patient populations to further establish its role in postoperative pain management.

Supplementary materials can be found via https://doi.org/10.3344/kjp.24346.

Permission to use the original illustration of defense and veterans pain rating scale has been obtained from the Defense & Veterans Center for Integrative Pain Management.

Data files are available from Harvard Dataverse: https://doi.org/10.7910/DVN/YYHJD3.

Ho-Jin Lee is a section editor for the Korean Journal of Pain; however, he has not been involved in the peer reviewer selection, evaluation, or decision process for this article. No other potential conflict of interest relevant to this article was reported.

This study was supported by the National R&D Program for Cancer Control through the National Cancer Center funded by the Ministry of Health & Welfare, Republic of Korea (No. RS-2023-CC140356).

Seungeun Choi: Writing/manuscript preparation; Taeyup Kim: Investigation; Hae Kyeong Yoo: Investigation; Sang-Youn Park: Writing/manuscript preparation; Soo-Hyuk Yoon: Data curation; Ho-Jin Lee: Supervision.

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