In asymptomatic patients where there is a very low clinical suspicion for splenomegaly, physical examination alone is unlikely to rule-in splenomegaly due to the inadequate sensitivity of the examination. Similar to many other findings in medicine, Castell's sign must be combined with clinical findings to rule in splenomegaly. To achieve a positive predictive value over 90%, the pretest probability must be 70%. Grover et al., recommends a greater than 10% preexamination clinical suspicion of splenic enlargement to effectively rule in the diagnosis of splenomegaly with physical exam. However, a 10% pretest probability only yields a positive predictive value of 35%.