The Role of Lactate Dehydrogenase to Albumin Ratio in Patients With Lower Respiratory Tract Infection

An old hospitalized patient lying in bed.
Researchers conducted a study to determine whether the lactate dehydrogenase to albumin ratio is an independent prognostic factor predictive of in-hospital mortality in patients with lower respiratory tract infection.

Among older patients with lower respiratory tract infection (LRTI), the lactate dehydrogenase to albumin (LDH/ALB) ratio may be an independent predictor for in-hospital mortality. These findings, from a retrospective review, were published in the American Journal of Emergency Medicine.

Patients (N=4592) diagnosed with LRTI between 2018 and 2020 at the Changnam National University Hospital in South Korea were retrospectively assessed for clinical characteristics and outcomes.

Among all patients included in the study, the median age was 71 (IQR, 55-80) years, 57.2% were men, 23.6% had diabetes, 19.1% had dementia, 16.4% had a history of stroke, and 15.4% had a malignancy. Of these patients, 3011 were hospitalized and 1524 were discharged. Among patients (n=234) admitted to the intensive care unit, the overall mortality rate was 3.6%.

The researchers noted that patients who died differed significantly in terms of demographic characteristics, vital signs, laboratory results, severity index scale scores, transfer status, and comorbidities (all P £.001). In addition, comorbidities that were not significantly different among these patients included heart failure (P =.339), chronic liver disease (P =.234), and chronic kidney disease (P =.152).

Compared with other albumin-based ratios and severity scales, the area under the receiver operating characteristic curve (AUC) for predicting in-hospital mortality was wider for the LDH/ALB ratio (AUC, 0.808; 95% CI, 0.757-0.842; P <.001). The researchers also calculated the AUC for other albumin-based ratios, including the blood urea nitrogen to albumin (BUN/ALB) ratio (AUC, 0.785; 95% CI, 0.758-0.811; P <.001), lactate to albumin ratio (AUC, 0.762; 95% CI, 0.733-0.781; P <.001), and C-reactive protein to albumin ratio (AUC, 0.729; 95% CI, 0.698-0.760; P <.001).

The researchers noted that the AUC for predicting in-hospital mortality was 0.781 for pneumonia severity index scores (95% CI, 0.734-0.789; P <.001); 0.656 for modified early warning scores (MEWS;95% CI, 0.624-0.699; P <.001); and 0.744 for confusion, uremia, increased respiratory rate, hypotension, and being older than 65 years (CURB-65) scores (95% CI, 0.717-0.771; P <.001).

The researchers performed a multivariate logistic regression analysis to determine the effect other variables had on the in-hospital mortality of LRTI. Variables found to be predictive of in-hospital included being older than 80 years (adjusted odds ratio [aOR], 4.74; 95% CI, 1.86-14.77; P =.003), being between 70 and79 years (aOR, 4.41; 95% CI, 1.74-13.68; P =.004), and oxygen saturations greater than 90% (aOR, 2.49; 95% CI, 1.80-3.45; P <.001). In addition, thrombocytopenia (aOR, 1.54; 95% CI, 1.11-2.14; P =.010), leukocyte counts of less than 4000 or greater than 12,000/mm3 (aOR, 1.50; 95% CI, 1.12-1.99; P =.006), MEWS (aOR, 1.11; 95% CI, 1.04-1.19; P =.001), BUN/ALB ratio (aOR, 1.03; 95% CI, 1.01-1.05; P =.003), and LDH/ALB ratio (aOR, 1.00; 95% CI, 1.00-1.00; P <.001) were also predictive of in-hospital mortality.

Compared with patients whose LDH/ALB ratio was less than 150, an LDH/ALB ratio between 150 and 250 was associated with an increased risk of in-patient mortality (aOR, 1.93; 95% CI, 1.35-2.77; P <.001), with a greater increased risk observed among those whose LDH/ALB ratio was greater than 250 (aOR, 4.15; 95% CI, 2.72-6.35; P <.001).

The ideal cutoff of the LDH/ALB ratio for in-hospital mortality was 166.3, with a sensitivity of 73.3%, specificity of 74.9%, positive predictive value of 30.2%, and negative predictive value of 95.0%.

This study was limited by its single center setting and retrospective design.

The researchers noted that “the LDH/ALB ratio showed better results compared with other albumin-based ratios and other severity scales.” They concluded that the “…LDH/ALB ratio could be used as an independent prognostic factor for the in-hospital mortality [of] patients [with LRTI].”


Lee B-K, Ryu S, Oh S-K, et al. Lactate dehydrogenase to albumin ratio as a prognostic factor in lower respiratory tract infection patients. Am J Emerg Med. 2021;52:54-58. doi:10.1016/j.ajem.2021.11.028