Critical study of observation of the sternal end of the right 4th rib.

Studies of the method of estimating age at death by the 4th rib exclusively concerned the phase method without fundamentally challenging the method as such. The present study analyzed observation of the variables on which the Iscan method is based. Ten observers made two assessments of the stage of pit depth, pit shape, rim and wall configurations of 59 right 4th ribs harvested from males (mean age: 49 years; range: 47-94 years). Observation showed poor reproducibility and repeatability for all three variables (Wilcoxon test, kappa-coefficient). Analysis of problem ribs revealed difficulty in measuring and imprecision in describing pit depth and failure to take account of continual aging for the other two variables. Despite these results, Iscan's variables provide objective information on age at death. It is recommended that the method be improved by better description of the variables and use of multivariate statistical analysis.