Value of the bell test and the hyperextension test for diagnosis in sciatica associated with disc herniation: comparison with Lasegue's sign and the crossed Lasegue's sign

Objectives. To evaluate the reliability, sensitivity, specificity and posit ive (PPV) and negative (NPV) predictive values for the diagnosis of sciatic a associated with disc herniation of the bell test (BT) and the hyperextens ion test (HT). Methods. According to magnetic resonance imaging, computed tomography scann ing or myelography findings, patients were classified as having sciatica as sociated with disc herniation (group A) or sciatica without disc herniation or sciatica of other mechanical origin (group B). Four clinical manoeuvres [bell test (BT). hyperextension test (HT), Lasegue's sign (LS) and the cro ssed Lasegue's sign (CL)I were tested by three investigators. Intra- and in terobserver reliabilities were calculated using the h correlation coefficie nt or the intraclass correlation coefficient (ICC). The sensitivity, specif icity, PPV and NPV of the four manoeuvres were calculated. Stepwise logisti c regression analysis was performed to determine the best set of variables predicting sciatica caused by disc herniation. Results. Seventy-eight patients (43 in group A, 35 in group B; 33 males) wi th a mean age of 50 +/- 16 yr were included, Interobserver reliabilities ra nged from 0.58 to 0.64 fur the BT, 0.35 to 0.50 for the HT, 0.27 to 0.47 fo r LS and 0.43 to 0.72 for CL. LS had the best sensitivity (0.77-0.83) and C L the best specificity(0.74-0.89). while PPV and NPV were equivalent for th e four manoeuvres (0.55-0.75 for PPV and 0.45-0.59 for NPV). The best PPV w as observed for the association of HT with CL (0.67-0.85). Stepwise logisti c regression analysis did not allow us to propose a set of variables predic ting sciatica caused by disc herniation. Conclusion. This study suggests that clinical values of the BT and HT are o f interest, and are similar to those of LS and CL.