Wang HY, Liu RJ, Wang YY, Wang DD, Zhang H, Zhang LJ, Jing X, Guo YJ, Li HQ, Liu AL, Ding XL. Phase angle as a predictor of malnutrition, sarcopenia, and adverse clinical outcomes in hospitalized patients with ulcerative colitis. World J Gastroenterol 2026; 32(42): 121556 [DOI: 10.3748/wjg.121556]
Corresponding Author of This Article
Xue-Li Ding, MD, Department of Gastroenterology, The Affiliated Hospital of Qingdao University, No. 16 Jiangsu Road, Qingdao 266003, Shandong Province, China. dingxueli@qdu.edu.cn
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Wang HY, Liu RJ, Wang YY, Wang DD, Zhang H, Zhang LJ, Jing X, Guo YJ, Li HQ, Liu AL, Ding XL. Phase angle as a predictor of malnutrition, sarcopenia, and adverse clinical outcomes in hospitalized patients with ulcerative colitis. World J Gastroenterol 2026; 32(42): 121556 [DOI: 10.3748/wjg.121556]
Hong-Ying Wang, Yue-Yuan Wang, Hao Zhang, Xue Jing, Ying-Jie Guo, Ai-Ling Liu, Xue-Li Ding, Department of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao 266003, Shandong Province, China
Ren-Juan Liu, Department of Gastroenterology, Weifang Yidu Central Hospital, Weifang 262500, Shandong Province, China
Dan-Dan Wang, Department of Clinical Nutrition, The Affiliated Hospital of Qingdao University, Qingdao 266003, Shandong Province, China
Li-Jun Zhang, Department of Population and Quantitative Health Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, United States
Han-Qing Li, Department of Gastroenterology, Qingdao Chengyang District People’s Hospital, Qingdao 266107, Shandong Province, China
Co-first authors: Hong-Ying Wang and Ren-Juan Liu.
Co-corresponding authors: Ai-Ling Liu and Xue-Li Ding.
Author contributions: Wang HY, Liu RJ, Jing X, Liu AL, and Ding XL participated in the conception and design of the study; Wang YY and Wang DD provided the research materials and patients; Wang HY, Liu RJ, Li HQ, Guo YJ, and Zhang H were involved in the collection, analysis or interpretation of the data; Wang HY and Liu RJ wrote the manuscript as co-first authors; Zhang LJ performed the statistical review and validation of the data analysis; Liu AL and Ding XL contributed equally as co-corresponding authors. All authors have read and approve the final manuscript.
AI contribution statement: AI tools (ChatGPT and DeepSeek) were used solely for linguistic refinement and formatting assistance. No AI tool was involved in the generation of research data, interpretation of results, or formulation of conclusions. All AI-generated outputs were critically reviewed and revised by the authors.
Supported by Beijing New Journey Foundation, No. 5503; and Clinical Medicine + X Research Project of the Affiliated Hospital of Qingdao University in 2024, No. QDFY+X2024212.
Institutional review board statement: This work was approved by the Ethics Committee of the Affiliated Hospital of Qingdao University, No. QYFY WZLL 42205.
Clinical trial registration statement: This study is a purely observational study without any health-related interventions, and therefore, trial registration was not required.
Informed consent statement: All participants offered informed written consent before enrollment.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
CONSORT 2010 statement: The authors have read the CONSORT 2010 Statement, and the manuscript was prepared and revised according to the CONSORT 2010 Statement.
Data sharing statement: All data are available from the corresponding author on reasonable request.
Corresponding author: Xue-Li Ding, MD, Department of Gastroenterology, The Affiliated Hospital of Qingdao University, No. 16 Jiangsu Road, Qingdao 266003, Shandong Province, China. dingxueli@qdu.edu.cn
Received: March 30, 2026 Revised: May 1, 2026 Accepted: June 24, 2026 Published online: November 14, 2026 Processing time: 178 Days and 13.4 Hours
Abstract
BACKGROUND
Malnutrition and sarcopenia are underrecognized yet clinically consequential comorbidities in hospitalized patients with ulcerative colitis (UC), each independently associated with poor clinical outcomes.
AIM
To evaluate phase angle (PhA) as a predictor of nutritional status, sarcopenia, and clinical outcomes in hospitalized patients with UC.
METHODS
This study prospectively enrolled 122 hospitalized patients with UC. PhA was measured by bioelectrical impedance analysis; nutritional status and sarcopenia were evaluated using the Global Leadership Initiative on Malnutrition criteria and the Asian Working Group for Sarcopenia 2019 criteria, respectively. Sex-specific PhA cut-off values for malnutrition and sarcopenia were derived from receiver operating characteristic curve analysis, and clinical outcomes were assessed at 12 and 54 weeks.
RESULTS
Mean PhA was 4.59° ± 0.97° in females and 5.55° ± 0.90° in males. Lower PhA was significantly associated with higher rates of malnutrition and sarcopenia (P < 0.001 for all) and correlated negatively with Global Leadership Initiative on Malnutrition grades (r = -0.578, P < 0.001) and Asian Working Group for Sarcopenia 2019 grades (r = -0.532,P < 0.001). On multivariate analysis, PhA independently predicted both conditions; optimal sex-specific cut-off values were 4.57° and 4.21° in females and 5.47° and 4.53° in males for malnutrition and sarcopenia, respectively. A combined PhA and prealbumin model achieved an area under the curve of 0.922 for sarcopenia detection. At 12 and 54 weeks, low PhA was associated with significantly worse clinical outcomes (P < 0.05).
CONCLUSION
PhA provides an objective, integrated assessment of nutritional status, sarcopenia, and clinical prognosis in hospitalized patients with UC and, in combination with prealbumin, achieves high predictive accuracy for sarcopenia.
Core Tip: Among hospitalized patients with ulcerative colitis, lower phase angle (PhA) values, derived from bioelectrical impedance analysis, were independently associated with greater prevalence of malnutrition and sarcopenia and with worsened disease outcomes. Sex-specific PhA cut-off values were established for identifying both conditions. Collectively, these findings position PhA as a practical, objective, and reliable clinical marker for nutritional and functional assessment in ulcerative colitis patient management.
Citation: Wang HY, Liu RJ, Wang YY, Wang DD, Zhang H, Zhang LJ, Jing X, Guo YJ, Li HQ, Liu AL, Ding XL. Phase angle as a predictor of malnutrition, sarcopenia, and adverse clinical outcomes in hospitalized patients with ulcerative colitis. World J Gastroenterol 2026; 32(42): 121556
Ulcerative colitis (UC) is a multifactorial inflammatory bowel disease characterized by chronic colonic and rectal inflammation. Its global incidence is rising steadily, imposing a considerable and growing economic burden on healthcare systems worldwide[1,2]. Malnutrition, sarcopenia, and micronutrient deficiencies are common manifestations in patients with UC[3] and each independently contributes to poor clinical outcomes[4,5]. Current assessment of nutritional status relies on established tools, including body mass index (BMI)[4], the European Society for Clinical Nutrition and Metabolism 2015 criteria[6], and the Global Leadership Initiative on Malnutrition (GLIM) criteria[4]. Sarcopenia is similarly diagnosed using widely adopted consensus frameworks such as the European Working Group on Sarcopenia in Older People criteria[7], the Asian Working Group for Sarcopenia 2019 (AWGS2019) criteria[8], and the American Sarcopenia Definitions and Outcomes Consortium criteria[9]. Many of these frameworks, however, are methodologically demanding and prone to inaccuracy in routine clinical settings, underscoring the need for a simpler, objective instrument that can reliably identify malnutrition and sarcopenia while also predicting adverse outcomes in patients with UC.
Derived from bioelectrical impedance analysis (BIA), the phase angle (PhA) is an objective and readily obtainable clinical parameter reflecting skeletal muscle mass (SMM), cellular quality, and membrane integrity[10]. In Crohn’s disease (CD), PhA has demonstrated predictive value for nutritional status and clinical outcomes[11] and correlates significantly with muscle mass, handgrip strength (HGS), and walk test performance, all established indicators of sarcopenia[12,13]. Nevertheless, its relationship with nutritional status and sarcopenia in adult hospitalized patients with UC remains poorly characterized. The present study therefore aimed to determine whether PhA represents a valid and practical index for identifying malnutrition and sarcopenia and for predicting adverse clinical outcomes in this population.
MATERIALS AND METHODS
Study population
This prospective single-center cohort study was carried out at the Affiliated Hospital of Qingdao University (Qingdao, China), where adult patients with UC admitted between September 2020 and February 2025 were consecutively evaluated for eligibility. Eligibility was determined on the basis of the following inclusion criteria: (1) Age of 18 years or older; (2) A diagnosis of UC confirmed in accordance with established diagnostic criteria; (3) Completion of BIA and HGS measurements; and (4) Availability of complete clinical data. Patients meeting any of the following criteria were excluded from the study: (1) Comorbidities associated with secondary sarcopenia, including malignant neoplasms, chronic kidney disease, severe hepatic impairment, or hyperthyroidism; (2) Conditions recognized to interfere with the accurate assessment of body composition, namely massive ascites or severe peripheral edema; (3) A history of major surgery or significant trauma within the three months preceding enrollment; or (4) Pregnancy or lactation.
Data collection
Baseline demographic and clinical data were collected for all participants, including sex, height, body weight at admission, and smoking and alcohol consumption history. UC disease severity was evaluated by the modified Mayo score, a validated composite index encompassing stool frequency, rectal bleeding, endoscopic findings, and the physician’s global assessment[14]. Patients were subsequently stratified into four disease activity categories according to the total score: Remission (≤ 2, with no individual sub-score exceeding 1), mild (3-5), moderate (6-10), and severe (11-12). At admission, a standardized set of laboratory parameters was measured for each participant, including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), albumin (Alb), prealbumin (PAB), total bilirubin, and hemoglobin (Hb).
BIA
Within 24 hours of enrollment, BIA was carried out by trained nutritionists using a portable bioelectrical impedance analyzer (InBody S10; Biospace Ltd., Seoul, Korea); all assessors were blinded to patients’ clinical and laboratory data, including disease activity scores and inflammatory markers. All measurements were obtained with participants in a barefoot standing position, with both hands and feet in full contact with the designated electrode sensors. From each assessment, five body composition parameters were derived: Fat-free mass (FFM), SMM, SMM index (SMI), bone mineral content (BMC), and PhA. PhA was computed at 50 kHz from resistance (R) and reactance (Xc) according to the equation: PhA (°) = arctan (Xc/R) × (180/π). Based on the Kyle criteria, low PhA was defined as values below 5.0° in males and below 4.6° in females at 50 kHz[15], and patients were accordingly classified into normal-PhA and low-PhA groups.
Assessment of nutritional status and sarcopenia
Nutritional risk was assessed within 24 hours of admission using the Nutritional Risk Screening 2002 (NRS 2002)[16], with a total score of ≥ 3 defined as indicative of nutritional risk. Malnutrition was subsequently diagnosed among at-risk patients according to the GLIM criteria[17]. Sarcopenia was identified based on the AWGS2019 criteria[8], requiring the coexistence of reduced SMM (SMI < 7.0 kg/m2 in males and < 5.7 kg/m2 in females) and impaired muscle function (HGS < 28 kg in males and < 18 kg in females)[8]. HGS, serving as the primary measure of muscle function, was quantified using a calibrated handheld dynamometer (BIOM-H500+X5; Biometrics, London, United Kingdom).
Clinical outcomes
Follow-up was performed at 12 and 54 weeks after discharge through telephone interviews or outpatient clinic visits, with all outcome assessors blinded to participants’ baseline PhA values. The 12-week timepoint was established to capture short-term treatment response, and the 54-week timepoint (approximately one year post-discharge) was established to evaluate the medium-term disease course and surgical risk, consistent with endpoints adopted in recent inflammatory bowel disease (IBD) cohort studies[18,19]. Three clinical outcomes were defined and documented throughout the follow-up period. Medication escalation was characterized as the advancement of therapy from aminosalicylates to glucocorticoids, thiopurines, biologics, or upadacitinib, while medication switching was characterized as transitions among glucocorticoids, biologics, and upadacitinib. Surgical intervention was recorded when operative management was required following the failure of conservative treatment. Hospital readmission was captured when re-hospitalization was necessitated by disease recurrence. Loss to follow-up was applied when both of the following conditions were met: (1) The patient was no longer receiving care at the study institution and outcome data were unobtainable from available medical records; and (2) The patient was unreachable following at least three telephone attempts on separate days or declined to provide follow-up information.
Statistical analysis
All statistical analyses were conducted in SPSS version 27.0 (SPSS Inc., Chicago, IL, United States) and R version 4.5.3 (http://www.r-project.org/). Normally distributed continuous variables are presented as mean ± SD and compared between groups by the independent samples t-test; non-normally distributed continuous variables were presented as median (Q1, Q3) and compared by the Mann-Whitney U test. Categorical variables were analyzed using the χ2 test or Fisher’s exact test, as appropriate. Associations between PhA and nutritional and sarcopenia-related parameters were examined using Pearson or Spearman correlation coefficients, selected according to the distributional properties of each variable. Independent risk factors for malnutrition and sarcopenia were identified by binary logistic regression. Variables found to be statistically significant (P < 0.05) on univariate analysis were entered into multivariate logistic regression models. Multicollinearity among candidate variables was assessed prior to model construction using the variance inflation factor, with values below 5 considered acceptable. The capacity of PhA to discriminate malnutrition and sarcopenia was evaluated by receiver operating characteristic curve analysis, performed separately for males and females, from which sex-specific cutoff values were derived. Model stability and optimism bias were addressed through bootstrap internal validation (1000 resamples). Statistical significance was set at a two-tailed P value of less than 0.05.
RESULTS
Baseline demographic and clinical characteristics
Of the 122 hospitalized patients with UC included in the final analysis, 48 were women (39.34%) and 74 were men (60.66%). Mean age and BMI were 44.77 ± 13.24 years and 21.12 ± 3.51 kg/m2 in women and 46.99 ± 14.62 years and 22.23 ± 3.19 kg/m2 in men, respectively. Men had significantly higher mean PhA (5.55° ± 0.90° vs 4.59° ± 0.97°), SMI, and HGS than women. Nutritional risk, malnutrition, and sarcopenia were identified in 53 (43.44%), 40 (32.79%), and 25 (20.49%) patients, respectively. Malnutrition prevalence and NRS 2002 scores differed significantly by sex, whereas sarcopenia prevalence did not. Further demographic and clinical characteristics are summarized in Table 1.
Table 1 Demographic, anthropometric, and clinical data of patients with ulcerative colitis, mean ± SD/n (%)/median (Q1, Q3).
Comparison of clinical and BIA parameters between PhA groups
Patients were stratified into low-PhA (n = 42, 34.43%) and normal-PhA (n = 80, 65.57%) groups. Compared with the normal-PhA group, the low-PhA group had significantly lower BMI, higher rates of nutritional risk, malnutrition, and sarcopenia, a greater proportion of severe disease, higher modified Mayo scores, and elevated CRP and ESR levels (P < 0.001 for all; modified Mayo scores: P = 0.002). Alb, PAB, and Hb levels and body composition parameters, including FFM, SMM, SMI, BMC and HGS, were also significantly lower in the low-PhA group (P < 0.05 for all). These findings are detailed in Tables 2 and 3.
Table 2 Comparison of patient characteristics in ulcerative colitis, mean ± SD/n (%)/median (Q1, Q3).
Table 3 Comparison of patient clinical data, and body composition between low and normal phase angle status in ulcerative colitis, mean ± SD/median (Q1, Q3).
Comparison of clinical and BIA parameters by malnutrition and sarcopenia status
Relative to their respective counterparts, patients with malnutrition and those with sarcopenia demonstrated markedly reduced PhA and significantly impaired nutritional status and body composition (P < 0.001 for both; Table 4). Specifically, BMI, FFM, SMM, BMC, Hb, Alb, and PAB were significantly lower in both groups, while disease activity scores and inflammatory markers, including CRP and ESR, were significantly elevated (P < 0.05 for all). Both conditions were also associated with greater prevalence of extraintestinal manifestations and IBD-related complications (P < 0.05 for all). Additionally, total bilirubin levels were significantly reduced in patients with sarcopenia (P = 0.003).
Table 4 Comparison of clinical data and body composition in ulcerative colitis, mean ± SD/n (%)/median (Q1, Q3).
Correlation of PhA with individual characteristics and BIA parameters
PhA demonstrated significant negative correlations with indicators of nutritional risk and disease severity, including NRS 2002 scores (r = -0.522, P < 0.001), GLIM grades (r = -0.578, P < 0.001), AWGS2019 grades (r = -0.532, P < 0.001), modified Mayo scores (r = -0.263, P = 0.003), CRP (r = -0.303, P = 0.001), and ESR (r = -0.512, P < 0.001). Conversely, PhA correlated positively with nutritional and body composition parameters, including Alb (r = 0.455, P < 0.001), PAB (r = 0.365, P < 0.001), FFM (r = 0.549, P < 0.001), BMC (r = 0.537, P < 0.001), and SMM (r = 0.586, P < 0.001). These associations are summarized in Table 5.
Table 5 Correlation between phase angle and individual characteristics/bioelectrical impedance analysis parameters.
Diagnostic efficacy of PhA in predicting malnutrition and sarcopenia
Univariate analysis identified female sex, lower BMI, higher modified Mayo scores, extraintestinal manifestations, IBD-related complications, elevated CRP and ESR, and lower Alb, PAB, Hb, FFM, SMM, BMC, and PhA as significant predictors of malnutrition (P < 0.05 for all). On multivariate analysis, lower PhA emerged as the sole independent predictor of malnutrition after adjustment for relevant covariates [odds ratio (OR) = 0.276, P = 0.007; Table 6]. In the sarcopenia model, variables constituting its diagnostic criteria were excluded to prevent circularity; lower PhA and lower PAB were independently associated with sarcopenia (OR = 0.270, P = 0.011 and OR = 0.970, P = 0.005, respectively; Table 7).
Table 6 Risk factors for malnutrition in patients with ulcerative colitis.
PhA value for predicting malnutrition and sarcopenia
Receiver operating characteristic curve analysis was conducted to determine optimal sex-specific PhA cut-off values for malnutrition and sarcopenia in this UC cohort, complementing the Kyle criteria used for descriptive group stratification. PhA demonstrated adequate discriminative performance for both conditions in both sexes (Figure 1). For malnutrition, areas under the curve (AUCs) were 0.880 (females: Cut-off 4.57°, sensitivity 85.7%, specificity 74.1%) and 0.807 (males: Cut-off 5.47°, sensitivity 78.9%, specificity 74.5%; P < 0.001 for both; Figure 1A and B). For sarcopenia, AUCs were 0.837 (females: Cut-off 4.21°, sensitivity 69.2%, specificity 85.7%) and 0.848 (males: Cut-off 4.53°, sensitivity 66.7%, specificity 98.4%; P < 0.001 for both; Figure 1C and D). PAB also predicted sarcopenia significantly, with an AUC of 0.835 (cut-off 196.75 mg/L, sensitivity 68.0%, specificity 88.7%; P < 0.001). A composite PhA-PAB model achieved an AUC of 0.922 (sensitivity 96.0%, specificity 85.6%; P < 0.001; Figure 1E), substantially outperforming either predictor alone.
Figure 1 Receiver operating characteristic curves for malnutrition and sarcopenia in ulcerative colitis patients.
A: Phase angle (PhA) values for malnutrition in females; B: PhA values for malnutrition in males; C: PhA values for sarcopenia in females; D: PhA values for sarcopenia in males; E: Different predictive indicators value for sarcopenia. PhA: Phase angle; PAB: Prealbumin; AUC: Area under the curve.
Bootstrap resampling with 1000 iterations was used for internal model validation. The combined PhA-PAB model for sarcopenia prediction yielded an AUC of 0.922, with bootstrap validation confirming negligible optimism (optimism = -0.002) and a bias-corrected AUC of 0.923 (95% confidence interval: 0.859-0.973; Table 8). Calibration was assessed via calibration curve and Brier score (0.091), indicating close agreement between predicted probabilities and observed outcomes (Figure 2).
Figure 2 Bootstrap internal validation of the combined model for predicting sarcopenia.
A: Bootstrap area under the curve distributions based on 1000 resamples; B: Calibration curve for the combined model.
Table 8 Bootstrap internal validation results for phase angle, prealbumin, and combined model.
All 122 patients completed 12-week follow-up, of whom 88 (72.1%) also completed 54-week follow-up. Compared with the normal-PhA group, the low-PhA group had significantly higher rates of medication escalation or therapeutic switching, hospital readmission, and surgical intervention at both time points (P < 0.05 for all; Table 9). Kaplan-Meier analysis further demonstrated that the low-PhA group had a significantly shorter median readmission-free interval at both 12 weeks (39 days vs 52 days; P = 0.034) and 54 weeks (69 days vs 134 days; P = 0.001) of follow-up (Figure 3).
Figure 3 Kaplan-Meier curve for readmission intervals in ulcerative colitis patients.
A: Time between readmission during 12 weeks; B: Time between readmission during 54 weeks.
Table 9 Comparison of clinical outcomes between low and normal groups under Kyle criteria, n (%).
To our knowledge, this is the first study to establish PhA as an independent predictor of both malnutrition and sarcopenia in adult hospitalized patients with UC. Furthermore, we demonstrate that reduced PhA is significantly associated with an increased risk of adverse clinical outcomes.
Malnutrition was identified in 32.79% of patients using the GLIM criteria, consistent with prior reports[20]. PhA differed significantly between malnourished patients and those with adequate nutritional status, and the low-PhA group exhibited a markedly higher incidence of malnutrition. While PhA has been established as a reliable nutritional indicator[21] and has demonstrated utility in patients with CD[11], and although its value as a malnutrition screening tool has been validated in hospitalized children with UC[22], evidence in adult inpatients with UC has been lacking. The present study addresses this gap directly. Sex-specific cut-off values of ≤ 5.47° for males and ≤ 4.57° for females were established to account for the well-documented sex difference in PhA, both achieving high sensitivity and specificity. Malnutrition impairs tissue electrical properties, thereby reducing PhA[23]. PhA reflects cell-membrane integrity and the distribution of body water between intracellular and extracellular compartments, offering a comprehensive index of body composition. Higher values correspond to greater cellularity, intact membranes, and preserved cellular function, whereas lower values are associated with adverse disease progression and poor prognosis[23,24]. Although hypoalbuminemia and systemic inflammation in hospitalized patients with UC may theoretically alter the extracellular-to-intracellular water ratio and influence PhA measurements, its clinical utility in IBD has been well established. Fernandes et al[25] further emphasized that PhA reflects cellular functionality and integrity in IBD patients beyond hydration status alone. Serum Alb, PAB, FFM, and BMI were each significantly lower in the low-PhA group and each correlated positively with PhA. Despite its widespread use as a nutritional marker, Alb also reflects inflammatory activity[26] and is susceptible to fluid redistribution, limiting its reliability as a standalone parameter. Similarly, although FFM decline is a recognized hallmark of malnutrition, and its directional concordance with decreasing PhA supports the association between low PhA and nutritional risk[27], FFM encompasses not only skeletal muscle but also bone, visceral organs, and other non-adipose tissues; total FFM may therefore remain within normal limits even when muscle function has already deteriorated[28]. BMI faces analogous limitations in diagnostic precision[29], particularly in older patients and those with specific disease-related conditions[30]. Collectively, the concordant reductions across these parameters provide multi-dimensional evidence of nutritional compromise, corroborating the predictive value of PhA. By integrating cellular-level functional information, PhA enhances diagnostic precision beyond what serum Alb and conventional screening instruments can offer, positioning it as a practical preliminary tool for predicting malnutrition and guiding nutritional intervention in patients with UC[31,32].
Sarcopenia was identified in 20.49% of patients, consistent with prior reports[33], and was significantly more prevalent in the low-PhA group. Sex-specific cut-off values of ≤ 4.21° for females and ≤ 4.53° for males achieved optimal sensitivity and specificity for sarcopenia prediction. Low PhA has previously been associated with higher sarcopenia prevalence in geriatric populations[34], likely reflecting progressive deterioration in muscle mass, strength, and function, compounded by fibrous tissue accumulation that further impairs muscle quality[10]. The present findings extend this evidence to patients with UC, confirming significant associations between PhA and AWGS2019 diagnostic grades, as well as positive correlations with two core diagnostic components, SMI and HGS[8], consistent with observations in liver cirrhosis[35]. Low PhA thus appears to reflect not only sarcopenia as a whole but also dysfunction across its individual components. This is mechanistically plausible: Sarcopenia reduces muscle reactance while fat mass accumulation elevates resistance, both of which lower PhA[35]. Because PhA simultaneously captures muscle quantity and quality, dimensions explicitly required by current sarcopenia guidelines[8], and endorsed by the EWGSOP2 consensus[36], it is well suited to the multidimensional assessment demands of contemporary sarcopenia frameworks. PAB was also identified as an independent predictor of sarcopenia, with a cut-off of ≤ 196.75 mg/L achieving high sensitivity and specificity. Its short half-life renders PAB a sensitive marker of short-term changes in protein intake and synthesis; low PAB has been associated with reduced SMI, diminished HGS, and impaired physical function[37], as well as with sarcopenia incidence in older hospitalized patients[38]. A composite PhA-PAB model substantially outperformed either marker alone, achieving a bias-corrected AUC of 0.923 on bootstrap internal validation (1000 iterations), with near-zero optimism confirming negligible overfitting. The calibration curve and Brier score further demonstrated close agreement between predicted probabilities and observed outcomes, supporting model reliability despite the relatively small sample size. Clinically, patients with UC exhibiting concurrently low PhA and PAB carry a substantially higher sarcopenia risk than those with a single abnormal parameter and should be prioritized for formal assessment and early nutritional intervention.
PhA correlated negatively with both CRP and ESR, which were significantly elevated in the low-PhA group, consistent with patterns reported in patients undergoing peritoneal dialysis[39]. The modified Mayo score was similarly higher in this group, corroborating prior evidence of an inverse relationship between PhA and disease activity in CD[11]. Mechanistically, inflammation and oxidative stress disrupt cellular structure and transmembrane fluid balance while impairing tissue electrical properties, collectively lowering PhA[23]. Taken together, these findings support PhA as a practical and informative indicator of inflammatory burden and disease activity in hospitalized patients with UC[39].
Adverse clinical outcomes were also more frequent in the low-PhA group, which exhibited significantly higher rates of hospital readmission, surgical intervention, and medication escalation or therapeutic switching, findings consistent with Kyle et al’s report[40] linking low PhA to prolonged hospitalization and with evidence of its independent prognostic value in CD and liver cirrhosis[41,42]. Kaplan-Meier analysis further confirmed shorter readmission-free intervals in the low-PhA group at both 12 and 54 weeks, extending the prognostic relevance of PhA across short- and medium-term horizons in UC. Persistent inflammation and nutritional depletion likely underlie this association by progressively compromising tissue electrical integrity and ultimately precipitating cell death[23]. These findings have direct clinical implications. Hospitalized patients with UC and low PhA should receive proactive, individualized nutritional intervention, encompassing dietary optimization, targeted micronutrient supplementation, and structured physical activity, as an integral component of routine management. Timely implementation of such measures may attenuate disease activity, enhance quality of life, and improve long-term prognosis.
This study has several notable strengths. To our knowledge, it is the first to establish PhA as an independent indicator of both malnutrition and sarcopenia in adult inpatients with UC, based on a prospectively enrolled cohort of 122 patients. The use of BIA in conjunction with the GLIM and AWGS2019 criteria provided a rigorous and comprehensive assessment of nutritional status and body composition. The study is not without limitations. Its single-center design limits generalizability, and multicenter validation across more diverse populations is warranted. Additionally, because PhA varies with sex and age, the SPA, which adjusts for both factors, may be more appropriate for cross-population comparisons; however, existing SPA reference values are derived from a Brazilian cohort[43] and are not directly applicable to Chinese patients. Developing SPA reference values specific to the Chinese population therefore remains an important goal for future research.
CONCLUSION
PhA is significantly lower in patients with malnutrition or sarcopenia and correlates strongly with key nutritional and functional parameters. Reduced PhA further independently predicts adverse clinical outcomes in hospitalized patients with UC. These findings establish PhA as a simple, objective tool for the integrated assessment of nutritional status, sarcopenia, and clinical prognosis in this population.
ACKNOWLEDGEMENTS
We would like to thank all participants in this project.
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