Researchers in Beijing have announced the development of a novel assessment tool, the Flu-IV Score, which predicts the need for invasive mechanical ventilation (IMV) in patients with influenza-related pneumonia (Flu-P) within 14 days of admission. The results of their multicenter study, conducted in in 5 tertiary hospitals in China, was recently published in BMC Pulmonary Medicine.

In the current study, 1107 patients with confirmed Flu-P were enrolled retrospectively from January 2012 to December 2019, including 895 patients in a derivation group and 212 patients in a validation group. Enrolled patients had a median age of 61 years and were 54.5% (603/1107) male. The most common comorbidities were cardiovascular disease (22.7%; 251/1107), diabetes mellitus (13.4%; 148/1107), and cerebrovascular disease (10.3%; 114/1107).

The predictive model was based on independent risk factors for IMV in the patients in the derivation cohort. Participants in the derivation cohort were divided into 2 groups based on whether they had undergone IMV within 14 days after admission. The researchers compared baseline characteristics between these 2 patient groups. The investigators incorporated all variables that produced a P <.1 in the first univariable analyses into a multivariable, backward stepwise logistic regression model to identify the risk factors related to 14-day IMV rates (which included age ≥65 years, influenza A virus infection, existence of solid malignant tumors, respiratory rate ≥30 breaths per minute, leukocyte count >10 × 109/L, leukocytes <0.8 × 109/L, albumin <35 g/L, arterial pH <7.35, ratio of partial pressure of oxygen in arterial blood to inspired oxygen fraction [PaO2/FiO2] <300 mmHg, early neuraminidase inhibitor [NAI] therapy, and systemic corticosteroids use at admission).


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A total of 10.6% (117/1107) of participants required IMV within 14 days of admission. The authors used a cumulative score of 5 points to identify patients at risk of IMV. Multivariate regression analyses showed that the most common factors associated with IMV included early NAI use (odds ratio [OR] 0.014; 95% CI, 0.003-0.083; P <.001; -3 points), lymphocytes <0.8 × 109/L (OR 5.755; 95% CI, 2.261-14.649; P <.001; 1 point), multilobar infiltrates (OR 4.568; 95% CI, 1.591-13.118; P =.007; 1 point), systemic corticosteroid use (OR 5.874; 95% CI, 2.356-14.642; P <.001; 1 point), age ≥ 65 years (OR 9.052; 95% CI, 3.544-23.119; P <.001; 1 point), PaO2/FiO2 <300 mmHg (OR 9.966; 95% CI, 3.619-27.447; P <.001; 2 points), respiratory rate ≥30 breaths per minute (OR 53.835; 95% CI, 19.711-147.033; P <.001; 3 points), and arterial pH <7.35 (OR 255.404; 95% CI, 42.701-527.608; P <.001; 4 points).

The Flu-IV Score had a sensitivity of 85.5% and a specificity of 88.8%. It showed better predictive performance than the ratio of oxygen saturation (ROX) index (area under the receiver operating characteristic curve [AUROC] = 0.909 vs 0.594; P =.004), modified ROX index (AUROC = 0.909 vs 0.633; P =.012), and heart rate, acidosis, state of consciousness, oxygenation, and respiratory rate (HACOR) scale (AUROC = 0.909 vs 0.622, P <.001) using the validation cohort.

One study limitation was the potential for selection bias due to the study’s retrospective design, which also resulted in an inability to recover and evaluate patient vaccination data or other missing information, possibly limiting the findings’ accuracy.

The authors found the Flu-IV score to be a valuable and reliable prediction tool for 14-day IMV rates in Flu-P patients. “This tool will help clinicians better evaluate the risks of early intubation for any given patient such that they can make optimal clinical judgments. However, it should be evaluated in more large-sample and prospective studies,” they noted.

Reference

Chen L, Han X, Li Y, Zhang C, Xing X. Flu-IV score: a predictive tool for assessing the risk of invasive mechanical ventilation in patients with influenza-related pneumonia. BMC Pulm Med. 2022;22(1):47. doi:10.1186/s12890-022-01833-2