Albumin-to-Globulin Ratio as a Predictor of Disease Severity in Emergency Department Patients Presenting with Flank Pain

Flank pain is a common emergency department (ED) presentation with a wide differential diagnosis. The albumin-to-globulin ratio (AGR) reflects both nutritional status and systemic inflammation, but its utility in pre-intervention ED patients with flank pain has not been systematically evaluated.

In this retrospective cross-sectional study, we included 291 consecutive adults who presented to the ED with flank pain and underwent urinary ultrasonography between August 2022 and May 2023. Severe presentation was defined as ≥2 of the following: hydronephrosis, acute kidney injury (creatinine >1.2 mg/dL), elevated CRP (>50 mg/L), or leukocytosis (WBC >12×10³/μL). Discriminative performance was assessed by receiver operating characteristic (ROC) analysis. Multivariable logistic regression was performed with adjustment for age, sex, urolithiasis, and log-NLR, deliberately excluding CRP, creatinine, and WBC to avoid incorporation bias. Incremental value beyond routinely available markers was assessed by comparing nested models containing CRP and creatinine, with and without AGR.

Among 291 patients (mean age 47.5 ± 23.5 years, 46% male), 59 (20.3%) had severe presentations. AGR was significantly lower in the severe group (1.26 ± 0.35 vs 1.55 ± 0.31, p < 0.001), with moderate discriminative ability (AUC 0.729; optimal cutoff ≤1.35; sensitivity 62.7%, specificity 77.2%). In multivariable analysis, AGR remained an independent predictor; each 0.1-unit decrease was associated with 18% higher odds of severe presentation (adjusted OR 1.18, 95% CI 1.04-1.34, p = 0.010). However, AGR did not improve discrimination beyond a model containing CRP and creatinine (ΔAUC = 0.000, p = 0.957). AGR did not differ between patients with and without urolithiasis (p = 0.14).

AGR is an independent predictor of severe presentation in ED patients with flank pain, but its moderate sensitivity and absence of incremental value beyond CRP and creatinine suggest it should be used as an adjunctive marker rather than a stand-alone screening tool. Prospective validation is needed before integration into ED triage algorithms.