Assessment of the serum and salivary free light chain levels in patients with proteinuria post cardiac surgery

Acute kidney injury (AKI) is a prevalent complication following cardiac surgery, affecting both short- and long-term survival rates. Proteinuria serves as an indicator of structural kidney damage and is increasingly recognized as a crucial marker for kidney disease and a risk factor for AKI. Free light chains (FLCs) are being investigated as potential markers for assessing the risk of kidney damage. This study aimed to validate the early detection of AKI by examining FLCs (kappa, lambda, and the kappa/lambda ratio) in serum and saliva samples. Clinical data were collected from 149 patients who underwent cardiac surgery in Baghdad, with 90 providing both saliva and serum samples for FLC evaluation. Patients were categorized based on the severity of proteinuria. Results showed that serum kappa levels were significantly elevated in patients with severe proteinuria compared to those with mild or no proteinuria. Conversely, salivary kappa levels were higher in patients with mild proteinuria than in those with severe or no proteinuria, while salivary lambda levels decreased as proteinuria severity increased. The rise in serum kappa may be attributed to immune system activation and kidney impairment. Both serum and salivary kappa demonstrated strong predictive capabilities for post-surgery AKI prognosis, outperforming lambda and the kappa/lambda ratio based on ROC analysis. The findings suggest that FLCs, particularly kappa, could be valuable in the early detection of AKI following cardiac surgery, highlighting their potential to enhance patient outcomes through proactive monitoring and intervention.