Estudio de determinación de beta-traza proteína en secreciones nasales para el diagnóstico de fístulas de líquido cefalorraquídeo

Abstract

A cerebrospinal fluid (CSF) leak to the sinonasal tract consists of a leak of CSF from the central nervous system into the rhinosinusal cavity, potentially severe due to the possibility of neuroinfection. There are different diagnostic modalities for the confirmation of a CSF leak among which the determination of beta-trace protein (?-TP) in nasal secretions stands out. Goals: - To determine a suitable cut-off point for the concentration of ß-TP in nasal secretions that allows the reliable diagnosis of a CSF leak. - To determine the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the ß-TP. - To assess the efficacy of the ß-TP test to confirm the closure of the CSF leaks. - To assess the effectiveness of imaging tests in the diagnosis of CSK leaks. - To determine the effect on the concentration of ß-TP of the use of swabs for nasal secretions collection. - To evaluate the influence of the presence of blood in the measure of ß-TP in nasal secretions. Methodology: - Nasal secretions samples were collected from patients whose clinical history is suggestive of CSF leak for the quantitative determination of ß-TP concentration. These values have been compared with the values of ?-TP obtained from two groups: o Nasal secretions from healthy volunteers without a clinical history of CSF leak. o Normal CSF samples without signs of inflammation. - Nasal secretions were collected using a swab placed in the nostril that is subsequently processed in a BN-ProSpec nephelometer determining the concentration of ?-TP. - The clinical history of patients with suspected CSF leak has been reviewed and a positive or negative diagnosis has been established (presence or absence of CSF leak). 21 of these patients have undergone more than one ?-TP determination to follow them up. - To assess the effect on the concentration of ß-TP of the use of swabs to obtain nasal secretions, 3 pools of CSF have been collected and diluted with 30%, 10%, 5% and 1% physiological saline. 2 mL of each dilution was impregnated on the swabs and the concentration of ?-TP in each pool and liquid extracted by nephelometry was measured. - To evaluate the influence of blood on the ß-TP measure in nasal secretions, we have collected a pool of nasal secretions and a pool of normal CSF that have been contaminated with a pool of blood in serial dilutions. The concentration of ?-TP has been determined for each of the dilutions by nephelometry. Results and conclusions: - The establishment of the cut-off value of the ß-TP concentration in nasal secretions of 1 mg/L allows the reliable diagnosis of a CSF leak when confirming the presence of CSF in nasal secretions with a sensitivity of 97%, a specificity 96%, a PPV of 98% and a NPV of 95%. - The determination of ß-TP in nasal secretions has confirmed the closure of the leak in all patients who have undergone serial determinations of ß-TP. - The imaging techniques that have been performed more frequently are CT and MRI. CT has shown greater diagnostic efficacy than MRI. - The collection of samples for the determination of the ß-TP in nasal secretions by means of a swab leads to an average increase in the concentration of ß-TP of 20%, that is why it is necessary to standardize its obtaining by means of a swab in order to apply our cut point. - The presence of blood in nasal secretions does not affect the critical values to differentiate CSF from nasal secretion.