Inter-observer agreement on the diagnosis of neurocardiogenic injury following aneurysmal subarachnoid hemorrhage

High Agreement and High Prevalence: The Paradox of Cohen's Kappa

Background:

Cohen's Kappa is the most used agreement statistic in literature. However, under certain conditions, it is affected by a paradox which returns biased estimates of the statistic itself.

Objective:

The aim of the study is to provide sufficient information which allows the reader to make an informed choice of the correct agreement measure, by underlining some optimal properties of Gwet’s AC1 in comparison to Cohen’s Kappa, using a real data example.

Method:

During the process of literature review, we have asked a panel of three evaluators to come up with a judgment on the quality of 57 randomized controlled trials assigning a score to each trial using the Jadad scale. The quality was evaluated according to the following dimensions: adopted design, randomization unit, type of primary endpoint. With respect to each of the above described features, the agreement between the three evaluators has been calculated using Cohen’s Kappa statistic and Gwet’s AC1 statistic and, finally, the values have been compared with the observed agreement.

Results:

The values of the Cohen’s Kappa statistic would lead to believe that the agreement levels for the variables Unit, Design and Primary Endpoints are totally unsatisfactory. The AC1 statistic, on the contrary, shows plausible values which are in line with the respective values of the observed concordance.

Conclusion:

We conclude that it would always be appropriate to adopt the AC1 statistic, thus bypassing any risk of incurring the paradox and drawing wrong conclusions about the results of agreement analysis.

Relationship between different surgical methods, hemorrhage position, hemorrhage volume, surgical timing, and treatment outcome of hypertensive intracerebral hemorrhage

BACKGROUND

The present study aimed to explore the relationship between surgical methods, hemorrhage position, hemorrhage volume, surgical timing and treatment outcome of hypertensive intracerebral hemorrhage (HICH).

METHODS

A total of 1 310 patients, who had been admitted to six hospitals from January 2004 to January 2008, were divided into six groups according to different surgical methods: craniotomy through bone flap (group A), craniotomy through a small bone window (group B), stereotactic drilling drainage (group C1 and group C2), neuron-endoscopy operation (group D) and external ventricular drainage (group E) in consideration of hemorrhage position, hemorrhage volume and clinical practice. A retrospective analysis was made of surgical timing and curative effect of the surgical methods.

RESULTS

The effectiveness rate of the methods was 74.12% for 1 310 patients after one-month follow-up. In this series, the disability rate was 44.82% 3-6 months after the operation. Among the 1 310 patients, 241 (18.40%) patients died after the operation. If hematoma volume was >80 mL and the operation was performed within 3 hours, the mortality rate of group A was significantly lower than that of groups B, C, D, and E (P<0.05). If hematoma volume was 50-80 mL and the operation was performed within 6-12 hours, the mortality rate of groups B and D was lower than that of groups A, C and E (P<0.05). If hematoma volume was 20-50 mL and the operation was performed within 6-24 hours, the mortality rate of group C was lower than that of groups A, B and D (P<0.05).

CONCLUSIONS

Craniotomy through a bone flap is suitable for patients with a large hematoma and hernia of the brain. Stereotactic drilling drainage is suggested for patients with hematoma volume less than 80 mL. The curative effect of HICH individualized treatment would be improved via the suitable selection of operation time and surgical method according to the position and volume of hemorrhage.