Coagulative function assessed preoperatively via the clot formation and lysis assay as a prognostic factor for blood loss in adolescents undergoing posterior spinal fusion for idiopathic scoliosis.

This is a single-institutional prospective observational cohort study with preoperative biospecimen banking. The aim of the study was to determine predictors of intra-operative blood loss using clinical factors, routine coagulation tests and the Clot Formation and Lysis (CloFAL) assay. The authors hypothesized that standard laboratory tests would not be predictive of blood loss but the CloFAL assay would be. Adolescents (10 – <21 years of age) presenting for posterior spinal fusion of idiopathic spinal scoliosis were enrolled and followed prospectively.


The following variables were found to be predictors of estimated blood loss (EBL): preoperative haemoglobin, number of vertebral levels fused, number of screws inserted, surgical duration and preoperative CloFAL analysis.  The CloFAL assay was able to differentiate between the groups with the highest and lowest quartiles of EBL by estimation of coagulation preoperatively. Standard preoperative laboratory measures of coagulation were not able to differentiate these 2 groups or predict which patients were at risk for an increased EBL.

Strengths and Limitations:

This is one of the largest prospective cohorts of adolescent idiopathic scoliosis patients studied. The demographics of the patients included in this study are similar to our patient populations. This is a single center study with low power and generalizability. The lack of international consensus on calculating EBL in scoliosis surgery may mean that blood loss was either over or underestimated in this study (median EBL was 13.8mL/ kg with 15% of patients receiving blood).

Take home message

Increased blood loss in scoliosis surgery is common. Predicting pre-operative clot formation and fibrinolysis may allow for improved risk stratification and appropriate planning. The utility of performing routine laboratory tests of coagulation function (PT, aPTT) may be questioned in terms of predicting EBL in adolescents presenting for idiopathic scoliosis correction. The CloFAL assay is currently limited to a research-based laboratory test. CloFAL cannot be used intra-operatively and its clinical use is yet to be determined. CloFAL may become useful as part of a preoperative risk stratification model in terms of predicting blood loss. Further testing of CloFAL is required to determine its clinical utility. Current laboratory measures of coagulation, as demonstrated in this single center study are not able to differentiate patients in terms of EBL & are less reliable than clinical factors in predicting EBL.

Reviewed by: Dr Neil Hauser