Letter to the Editor

Dear Sir,

We read with interest the recently published article by Rifai and colleagues [1] on the assessment of liver and spleen stiffness by ultrasonic elastography with the Acoustic Radiation Force Impulse (ARFI) system in patients with chronic liver disease and their possible correlates with portal hypertension and various clinical and demographic variables.

Two main relevant findings appeared to be the inferiority of splenic stiffness in comparison to liver stiffness for the identification of patients with portal hypertension and the presence of a positive statistically significant correlation between splenic stiffness and age. Unfortunately, we believe that these two issues have not been properly analysed and deserve a comment, since the former is to us misleading and the latter flawed by a statistical bias.

Regarding the first point, the near totality of patients included in the portal hypertension group had histologically proven cirrhosis (and it might be speculated that also the few others with portal hypertension were already cirrhotic), whereas in the group of chronic liver disease without portal hypertension the near totality suffered from chronic hepatitis without cirrhosis. Therefore, it appears to us that the main message of the study is that splenic stiffness is inferior to liver stiffness for the diagnosis of cirrhosis rather than for portal hypertension. In fact, the question about the presence of portal hypertension and thus the role of elastosonographic techniques for its detection, is meaningful only in case of cirrhosis, but not in case of chronic hepatitis, as these patients do not suffer from portal hypertension by definition (thus no additional tool to exclude portal hypertension is strictly required). Indeed their values of splenic stiffness were identical to those of normal controls. Thus, a more appropriate study protocol to the aim of evaluating the relationship between splenic elastosonography and portal hypertension would imply the assessment of only patients with cirrhosis (or at least sever fibrosis) using as gold standard for the diagnosis of portal hypertension the measurement of hepatic venous pressure gradient, as a recently published article did [2].

Regarding splenic stiffness and age, which were found to be positively correlated both at univariate and multivariate analyses we believe a statistical bias and not true information is the basis for this finding. The authors, in fact, pooled together patients and controls (in Fig. 1b of their study we counted a number of circles corresponding to the number of subjects of all three groups pooled together and not only of patients with chronic liver disease). However, the age of patients and controls was significantly different, as controls were much younger than patients, 38 years vs. 48 – 49 years. Therefore, a pooled analysis is not acceptable and clearly the association appears determined by the fact the older patients were also those affected by cirrhosis and portal hypertension, thus determining a positive correlation. To verify this problem we decided to analyse patients investigated in our unit with splenic ARFI elasto-sonography in the last two years within research protocols, partially included already in a previous publication [3]. We identified 73 patients, the very large majority (89 %) of these affected by cirrhosis, the remaining by METAVIR F3 fibrosis, with a mean age of 60 ± 10 years. No correlation between splenic stiffness and age was found (r = –0.011, p = 0.926), confirming that a bias is probably the cause for the finding in the Rifai’s study [1] and that no correlation between splenic stiffness and age exists, at least in chronic liver disease.

Yours sincerely

Fabio Piscaglia, MD PhD

Alberto Borghi, MD PhD

Veronica Salvatore, MD PhD

Sara Marinelli, MD

Eleonora Terzi, MD

Laura Venerandi, MD

Chiara Palamà, MD

Division of Internal Medicine, Department of Medical and Surgical Sciences, University of Bologna, Via Albertoni 15, 40 138, Bologna, Italy

• References

• 1 Rifai K, Cornberg J, Bahr M et al. ARFI elastography of the spleen is inferior to liver elastography for the detection of portal hypertension. Ultraschall in Med 2011; 32: E24-E30
• 2 Colecchia A, Montrone L, Scaioli E et al. Measurement of Spleen Stiffness to Evaluate Portal Hypertension and the Presence of Esophageal Varices in Patients With HCV-Related Cirrhosis. Gastroenterology 2012; 143: 646-654
• 3 Piscaglia F, Salvatore V, Di Donato R et al. Accuracy of VirtualTouch Acoustic Radiation Force Impulse (ARFI) imaging for the diagnosis of cirrhosis during liver ultrasonography. Ultraschall in Med 2011; 32: 167-175