We have read with great interest the article by Ruiz-Bocos et al.,1 titled "Early identification of hypofibrinogenemia in major trauma: The usefulness of the FiT-6 (Fibrinogen in Trauma-6) score," publushed in Medicina Intensiva. We commend the authors' valuable work in developing a practical tool for the early prediction of hypofibrinogenemia in trauma. However, we have several key concerns regarding the study's methodological design and the clinical applicability of its findings.

First, our primary concern relates to the method of fibrinogen measurement used in the study. While the authors commendably acknowledge in their limitations section that the PT-derived method may overestimate fibrinogen levels, we believe the profound impact of this methodological choice on the study's core conclusions is significantly understated. It is well-established that in the context of trauma-induced coagulopathy (TIC), the PT-derived method systematically overestimates functional fibrinogen levels due to the presence of high levels of fibrinogen/fibrin degradation products (FDPs), and dysfibrinogenemia.2 The Clauss method is widely recognized as the gold-standard functional assay. The study's reliance on a measurement technique known to be biased in the target patient population may have introduced significant misclassification bias. A proportion of patients whose fibrinogen levels were truly below the threshold of 203 mg/dL may have been incorrectly assigned to the normal group due to overestimation by the PT-derived method. This systematic bias could have artificially widened the gap between the hypofibrinogenemia and normal groups, potentially leading to a falsely inflated measure of the model's discriminative ability, as reflected by the area under the receiver operating characteristic curve (AUC).

Second, this methodological uncertainty raises serious questions about the FiT-6 score's clinical utility, particularly its low Positive Predictive Value (PPV). The authors report a PPV of only 33.3% for a score of ≧3. While the AUC of 0.90 is impressive, this PPV figure indicates that among patients classified as high-risk by the score, two-thirds (approximately 67%) did not actually develop hypofibrinogenemia. Such unnecessary intervention not only increases healthcare costs but, more importantly, exposes a large number of patients to potential iatrogenic risks, including thromboembolic events and transfusion-related complications. The value of an early warning tool with a high false-positive rate is questionable when it is intended to guide critical therapeutic decisions.

In conclusion, although the FiT-6 score is conceptually appealing, its interpretation warrants caution. Its foundation on a potentially inaccurate fibrinogen measurement method and its inherent limitation of a low PPV necessitate external validation using the Clauss method before it can be reliably adopted into clinical practice. Until more robust evidence is available, the FiT-6 score may be better suited as a rule-out tool given its likely high Negative Predictive Value, rather than a rule-in tool for initiating therapy.