The predictive value of the lactate/albumin ratio combined with APACHE II and injury severity score for short-term prognosis in patients with polytrauma

Abstract

Background

Polytrauma is the simultaneous or sequential occurrence of injuries. Current prognostic indicators of this condition have limitations. This study aimed to investigate the correlation between lactate/albumin ratio (LAR) and short-term prognosis in polytrauma patients and evaluate the predictive value of combining LAR with the Acute Physiology and Chronic Health Evaluation II (APACHE II) and Injury Severity Score (ISS).

Methods

Clinical data from 113 polytrauma patients admitted to the intensive care unit of the Second People’s Hospital of Hefei(February 2019–July 2024) were analyzed. Receiver operating characteristic (ROC) curves were used to assess the predictive performance of the LAR, APACHE II, ISS, and their combinations. Logistic regression identified risk factors for poor prognosis.

Results

ROC analysis showed strong predictive value for poor short-term prognosis by APACHE II (area under the curve [AUC] = 0.931), ISS (AUC = 0.812), and LAR at 48 h (AUC = 0.901; all P < 0.05). The combination of APACHE II, ISS, and LAR at 48 h demonstrated superior predictive value (AUC = 0.968, P < 0.01). Logistic regression confirmed that APACHE II, ISS, and LAR at 48 h were independent risk factors for poor prognosis (all P < 0.05).

Conclusion

LAR is correlated with short-term prognosis in patients with polytrauma. APACHE II, ISS, and LAR at 48 h are independent risk factors with strong individual predictive values, and their combination provides greater predictive power.

Introduction

Trauma is a major global public health concern. Trauma-related deaths account for 8% of the total annual deaths [1]. Polytrauma is generally defined as the simultaneous or sequential occurrence of injuries to two or more anatomical regions or organs caused by the same injurious factor, with at least one life-threatening injury [2]. Polytrauma is associated with high mortality and disability rates, poses a serious threat to human health, and imposes a significant burden on society. Polytrauma has three peak mortality periods: the first occurs within minutes to one hour after the injury, the second within 6–8 h after the injury, and the third within 1–4 weeks after the injury. With advancements in medicine and the establishment of trauma centers, the second and third mortality peaks have decreased significantly. However, reports indicate that over 10% of the patients die during these periods [3].

Lactate reflects the body’s tissue oxygen supply and metabolic state and is often used as a risk factor for assessing the prognosis of critically ill patients [4]. Studies have shown that lactate levels are associated with the prognosis of polytrauma [5]. However, lactate lacks specificity, as conditions such as liver dysfunction can also lead to abnormal increases in lactate levels [6]. Therefore, relying solely on lactate levels for prediction has limited value.

Albumin is the main protein in the human plasma and plays an important role in maintaining colloid osmotic pressure, anti-inflammatory responses, and substance transport. It is also a key indicator of nutritional status. Although the literature has long indicated that albumin levels are associated with the prognosis of polytrauma [7], relying solely on albumin levels for prediction lacks specificity.

In recent years, some studies have demonstrated the predictive value of the lactate/albumin ratio (LAR) for severe diseases such as sepsis and acute pancreatitis [8–10]. This composite indicator has better accuracy than single indicators. Although LAR has been validated in conditions such as sepsis, current evidence remains scant regarding its predictive value for patients with polytrauma The Acute Physiology and Chronic Health Evaluation II (APACHE II) and Injury Severity Score (ISS) are the most commonly used indicators for assessing the condition of patients with polytrauma, and their prognostic value has been proven [11–13]. However, APACHE II only focuses on the worst indicators within 24 h of admission and cannot dynamically reflect changes in the patient’s condition or the impact of treatment on prognosis. The ISS tends to overlook the impact of non-fatal injuries on prognosis and lacks an assessment of physiological status. Therefore, this study aimed to dynamically monitor LAR in patients with polytrauma, analyze its correlation with short-term prognosis, and combine LAR with APACHE II and ISS to compensate for the limitations of individual indicators. Since LAR is readily accessible in clinical practice, once its predictive value is confirmed, it will be more conducive to the implementation of clinical work. Furthermore, dynamic monitoring of LAR combined with the two well-established metrics, APACHE II and ISS, could potentially enhance prediction accuracy. This approach aimed to provide a theoretical foundation for the development of clinical prevention and treatment strategies.

Methods

General information

Clinical data were collected from 113 patients with polytrauma admitted to the Intensive Care Unit of the Second People’s Hospital of Hefei between February 2019 and July 2024. Among them, 77 were male and 36 were female, aged 16–90 years, with an average age of 50.12 ± 16.83 years. Based on the 28-day prognosis, the patients were divided into a survival group (n = 86) and a death group (n = 27). Inclusion criteria: Patients diagnosed with polytrauma according to the diagnostic criteria laid out in “The new Berlin definition of polytrauma” [14] (included: a patient with an Abbreviated Injury Scale ≥ 3 for two or more different body regions and with one or more additional parameters from the following: (1) A Glasgow Coma Scale ≤ 8; 2. Systolic blood pressure ≤ 90 mmHg; 3. Partial thromboplastin time ≥ 40 s or international normalized ratio ≥ 1.4; 4. Age ≥ 70 years); (2) Age ≥ 16 years; (3) Admitted to the intensive care unit (ICU) within 6 h after injury; (4) Complete clinical data. The exclusion criteria were as follows: (1) death within 3 days of admission; (2) history of severe heart, liver, or kidney diseases, malignant tumors, or immune system diseases), and (3) use of medications such as metformin or acetaminophen that may cause elevated lactate levels within the past month. This study was approved by the Clinical Trial Ethics Committee of Hefei Second People’s Hospital (Approval No. 2025-Research-019). All the patients received treatment according to the principles of damage control resuscitation.

Research methods

Clinical data were collected, including sex, age, APACHE II, ISS, lactate, and albumin levels measured upon ICU admission and at 24 and 48 h. The corresponding LAR was calculated for each time point, and the 24-h lactate clearance rate was determined based on the lactate level at admission and 24 h post-treatment.

Statistical analysis

Statistical analyses were performed using SPSS (version 29.0) and R software (version 4.2.3), with the significance threshold set at P < 0.05. Normally distributed continuous data are expressed as mean ± standard deviation (x̄ ± s), whereas non-normally distributed data are presented as median (P25, P75). Independent sample t-tests were used for normally distributed data, and non-parametric tests were used for non-normally distributed data. The predictive values of APACHE II, ISS, lactate, albumin, LAR, lactate clearance rate, and combined indicators (integrating APACHE II, ISS, and LAR at 48 h after treatment) for short-term prognosis in polytrauma were evaluated using receiver operating characteristic (ROC) curve analysis. Internal validation was conducted using the bootstrap method (1000 resamples, random seed = 123) to adjust the area under the curve (AUC) confidence intervals. Spearman’s correlation analysis was used to assess whether LAR was a potential risk factor for short-term prognosis. Logistic regression models were constructed to analyze the influence of APACHE II, ISS, and LAR at 48 h on short-term outcomes, with the results corrected using 1000 bootstrap resamples. Additionally, variance inflation factor (VIF) testing was performed using the ‘car’ package in R to evaluate the multicollinearity among APACHE II, ISS, and LAR at 48 h in the logistic regression model.

Results

Comparison of baseline data between groups

There were statistically significant differences between the survival and death groups in age; APACHE II score; ISS; and lactate, albumin, and LAR levels at admission, 24 h after treatment, and 48 h after treatment (all P < 0.05). However, there was no significant difference in sex between the two groups (P > 0.05) (Table 1).

Table 1.

Baseline data of patients with polytrauma

Indicator	Survival group (n = 86)	Death group (n = 27)	P-value
Age (years)	48.01 ± 16.51	56.54 ± 16.44	0.01
Sex (Male/Female)	58/28	19/8	0.67
APACHE II	13.86 ± 6.42	27.71 ± 6.58	< 0.01
ISS	23.39 (18.0, 26.0)	31.14 (25.0, 34.0)	< 0.01
Lactate at Admission (mmol/L)	4.06 (2.13, 5.11)	5.61 (3.19, 7.00)	0.01
Lactate at 24 h (mmol/L)	2.43 (1.26, 3.25)	5.60 (2.50, 8.55)	< 0.01
Lactate at 48 h (mmol/L)	1.42 (0.77, 1.62)	5.18 (2.38, 5.12)	< 0.01
Albumin at Admission (g/L)	34.70 ± 6.25	31.93 ± 8.47	0.03
Albumin at 24 h (g/L)	32.26 ± 5.35	29.84 ± 6.41	0.02
Albumin at 48 h (g/L)	31.86 ± 4.31	28.13 ± 4.70	< 0.01
LAR at Admission	0.13 (0.06, 0.15)	0.23 (0.08, 0.23)	< 0.01
LAR at 24 h	0.08 (0.04, 0.10)	0.22 (0.06, 0.27)	< 0.01
LAR at 48 h	0.05 (0.02, 0.05)	0.21 (0.08, 0.20)	< 0.01

ISS Injury Severity Score

ROC analysis of age, APACHE II, ISS, lactate, albumin, lactate clearance and LAR for predicting poor short-term prognosis in polytrauma

Bootstrap-corrected ROC curve analysis revealed that APACHE II, ISS, and LAR at 48 h after treatment had strong predictive values for poor short-term prognosis in polytrauma patients (AUC: 0.931, 0.812, and 0.901, respectively; all P < 0.05). The combination of APACHE II, ISS, and LAR 48 h after treatment had an even better predictive value for short-term prognosis in polytrauma patients (AUC: 0.968, P < 0.01) (Fig. 1, Table 2).

Fig. 1.

ROC analysis of age, APACHE II, ISS, lactate, albumin, lactate clearance rate, LAR, and combined indicators for predicting poor short-term Prognosis in Polytrauma. APACHE II Acute Physiology and Chronic Health Evaluation II; ISS Injury Severity Score; LAR lactate/albumin ratio; ROC receiver operating characteristic

Table 2.

ROC analysis of age, APACHE II, ISS, lactate, albumin, lactate clearance rate, LAR and combined indicators for predicting poor short-term prognosis in polytrauma (bootstrap-corrected)

Indicator	AUC	Standard Error	P-value	95% CI	Cut-off Value	Sensitivity	Specificity
Age (years)	0.636	0.61	0.03	0.517–0.755	57.5	0.500	0.765
APACHE II	0.931	0.020	< 0.01	0.884–0.977	22.5	0.857	0.894
ISS	0.812	0.040	< 0.01	0.735–0.889	20.5	1	0.565
Lactate at Admission (mmol/L)	0.663	0.060	0.04	0.548–0.777	4.745	0.571	0.718
Lactate at 24 h (mmol/L)	0.742	0.060	< 0.01	0.624–0.860	4.795	0.500	0.929
Lactate at 48 h (mmol/L)	0.886	0.040	< 0.01	0.811–0.960	2.08	0.857	0.847
Albumin at Admission (g/L)	0.596	0.070	0.15	0.466–0.726	32.25	0.571	0.659
Albumin at 24 h (g/L)	0.606	0.060	0.10	0.480–0.732	32.35	0.679	0.529
Albumin at 48 h (g/L)	0.704	0.060	< 0.01	0.593–0.814	28.75	0.536	0.800
LAR at Admission	0.667	0.060	0.04	0.550–0.784	0.183	0.464	0.859
LAR at 24 h	0.749	0.060	< 0.01	0.635–0.862	0.087	0.714	0.718
LAR at 48 h	0.901	0.030	< 0.01	0.838–0.965	0.074	0.857	0.859
lactate clearance	0.658	0.06	< 0.01	0.544–0.772	0.521	0.329	0.929
Composite Index	0.968	0.010	< 0.01	0.939–0.996	0.882	0.964	0.918

ROC receiver operating characteristic; APACHE II Acute Physiology and Chronic Health Evaluation II; ISS Injury Severity Score; LAR lactate albumin ratio

Spearman correlation analysis of dynamic changes in LAR levels and short-term prognosis in polytrauma

Spearman’s correlation analysis showed that LAR levels at admission, 24 h after treatment, and 48 h after treatment were all correlated with poor short-term prognosis in polytrauma patients (Rs: 0.250, 0.372, and 0.600, respectively; all P < 0.05). LAR was identified as a potential risk factor for poor short-term prognosis in patients with polytrauma, with the strongest correlation observed 48 h after treatment (Table 3).

Table 3.

Spearman correlation analysis of dynamic changes in LAR levels and short-term prognosis in polytrauma

	LAR at admission	LAR at 24 h	LAR at 48 h
Rs	0.250	0.372	0.600
P-value	0.01	< 0.01	< 0.01

LAR lactate albumin ratio

Binary logistic regression analysis of APACHE II, ISS, and LAR at 48 h after treatment for short-term prognosis in polytrauma

Binary logistic regression models were constructed using APACHE II, ISS, and LAR. Due to collinearity between LAR at ICU admission and 24 and 48 h post-treatment, Spearman correlation analysis showed the strongest association between LAR at 48 h and poor short-term outcomes; and only LAR at 48 h post-treatment was included in the final model. The results identified APACHE II, ISS, and LAR at 48 h as significant independent risk factors for adverse short-term prognosis (all P < 0.05) (Table 4).

Table 4.

Binary logistic regression analysis of APACHE II, ISS, and LAR at 48 h for short-term prognosis in polytrauma (bootstrap-corrected)

Factor	β	Standard Error	Wald X2	P-value	OR	95% CI
APACHE II	0.257	0.07	11.94	< 0.01	1.293	0.137–0.473
ISS	0.114	0.05	5.45	0.02	1.121	− 0.055–0.259
LAR at 48 h	17.34	6.78	6.54	< 0.01	33,828,720.52	1.157–46.049

APACHE II Acute Physiology and Chronic Health Evaluation II; ISS Injury Severity Score; LAR lactate albumin ratio; CI confidence interval

VIF testing: APACHE II, ISS, and LAR at 48 h after treatment

VIF testing revealed variance inflation factors of 1.02 for APACHE II, 1.08 for ISS, and 1.06 for LAR at 48 h (Table 5). All VIF values were substantially below the conventional threshold of 5 (where VIF > 5 typically indicates significant multicollinearity) and approached 1.0, demonstrating negligible multicollinearity among the independent variables. Consequently, the APACHE II, ISS, and 48-h LAR maintained strong independence within the logistic regression model, yielding stable coefficient estimates that were unaffected by collinearity.

Table 5.

VIF testing: APACHE II, ISS, and LAR at 48 h after treatment

Factor	VIF
APACHEII	1.02
ISS	1.07
LAR at 48 h	1.06

VIF variance inflation factor; APACHE II Acute Physiology and Chronic Health Evaluation II; ISS Injury Severity Score; LAR lactate albumin ratio

Discussion

Patients with polytrauma often have elevated lactate levels, which may result from factors such as the hypoxia and increased anaerobic metabolism from hemorrhagic or traumatic shock. Alternatively, systemic inflammatory responses may release large amounts of inflammatory mediators, causing microcirculatory dysfunction and exacerbating tissue hypoxia and lactate production [15, 16]. Organ dysfunction, particularly liver damage, can reduce lactate clearance, leading to elevated lactate levels [17]. Additionally, extensive muscle cell damage may trigger the release of lactate, and poorly controlled infections in patients with polytrauma can progress to sepsis or septic shock, further increasing the lactate levels [18]. During the treatment of patients with polytrauma, the use of certain medications, such as epinephrine, can promote glycolysis and increase lactate levels [19]. Clinically, lactate levels have long been used as a predictor of prognosis in patients with polytrauma [20]. However, elevated lactate levels in these patients are influenced by multiple factors, which limits the predictive value of relying solely on lactate levels. Similarly, albumin levels are closely related to the prognosis of critically ill patients [21]; however, albumin levels in polytrauma patients are also influenced by multiple factors, making single indicators insufficient for accurate prediction. LAR, as a composite indicator, has been widely used in recent years to assess the prognosis of critically ill patients and is less susceptible to interference from multiple factors than single indicators such as lactate [10]. APACHE II, one of the most commonly used scoring systems for critically ill patients, assesses acute physiology, age, and chronic health status, and has been widely validated as a prognostic indicator of trauma patients [22]. However, it lacks a dynamic assessment of post-treatment conditions, which limits its predictive value [23]. The ISS is the most commonly used tool for assessing the severity of polytrauma and is considered the gold standard in trauma medicine [24]. However, ISS focuses more on assessing life-threatening injuries, overlooking the impact of non-fatal injuries on prognosis, and lacks physiological indicators, which limits its predictive value [25].

This study analyzed data from 113 patients with polytrauma and found that LAR was correlated with short-term prognosis, suggesting that LAR may be a potential risk factor for poor short-term prognosis. ROC curve analysis showed that LAR at admission, 24 h after treatment, and 48 h after treatment had better predictive values than lactate or albumin alone at the same time points. LAR 48 h after treatment had the highest AUC value (0.901; P < 0.05). APACHE II and ISS also showed excellent predictive values for short-term prognosis in polytrauma patients, with AUCs of 0.931 and 0.812, respectively (both P < 0.05). However, considering the limitations of these indicators and their inability to dynamically reflect changes in patient condition or the impact of treatment on prognosis, the combination of LAR 48 h after treatment with APACHE II and ISS had an AUC of 0.968 (P < 0.05), which was higher than that of any single indicator alone, indicating that the combined indicator has a better predictive value for short-term prognosis in polytrauma patients. Spearman’s correlation analysis of LAR levels at admission, 24 and 48 h after treatment suggested that LAR may be a potential risk factor for poor short-term prognosis in patients with polytrauma, with the strongest correlation observed at 48 h after treatment. Binary logistic regression analysis of LAR at 48 h after treatment, APACHE II, and ISS showed that all three were independent risk factors for poor short-term prognosis in patients with polytrauma patients. VIF testing confirmed that the variance inflation factors for APACHE II, ISS, and LAR at 48 h approached 1.0, indicating negligible multicollinearity among these three predictors. This finding supports the stability of the estimated regression coefficients in the model.

Conclusions

In conclusion, the LAR, APACHE II, and ISS are all associated with short-term prognosis in patients with polytrauma, and their combined use provides a better predictive value. Therefore, clinicians should monitor changes in LAR levels in patients with polytrauma and use APACHE II and ISS to comprehensively assess patient condition and adjust treatment plans in a timely manner, potentially reducing the occurrence of poor prognosis. However, this study has several limitations. The single-center design and modest sample size (n = 113) may restrict the generalizability of the results. External validation of the combined model is required to mitigate the risk of overfitting. The temporal dynamics of LAR beyond 48 h remains largely unexplored, potentially missing a critical prognostic shifts. Additionally, excluding early deaths (< 72 h) may underestimate driver mortality. Future multicenter studies should address these gaps, incorporate LAR measurements, and validate the model in injury-specific cohorts.

Abbreviations

AIS

Abbreviated Injury Scale

APACHE II

Acute Physiology and Chronic Health Evaluation II

AUC

Area under the curve

ICU

Intensive care unit

ISS

Injury Severity Score

LAR

Lactate/albumin ratio

ROC

Receiver operating characteristic

VIF

Variance inflation factor

Author contributions

Xiaobo Zhao and Li Yao designed and performed the study. Xiaobo Zhao analyzed the data. All authors contributed to the editorial changes in the manuscript. All the authors have read and approved the final version of the manuscript. All authors participated sufficiently in the study and agreed to be accountable for all aspects.

Funding

Not applicable.

Data availability

The data used to support the findings of this study are available from the corresponding author upon request.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the Declaration of Helsinki. This study was approved by the Medical Ethics Committee of The Second People’s Hospital of Hefei, China. The principle of informed consent was followed throughout the experiment; information about the study was provided to the patients or their families, and consent was obtained.

Competing interests

The authors declare no competing interests.