Changes in S100B levels rather than absolute values may be a better marker of severity of septic encephalopathy
TX, USA
* E-mail: joana.k.panni{at}uth.tmc.edu
Editor—We read with interest the article by Piazza and colleagues,1 where they report that elevated S100B levels did not correlate with the severity of encephalopathy during sepsis. We would like to ask the authors that even though the S100B levels did not correlate with the severity of encephalopathy on ICU admission, whether the rate of increase in serum S100B levels could be indicative of severity of encephalopathy. The time of ICU admission is a variable in itself, in terms of when the duration of sepsis began. In fact, a third of the patients, three with GCS scores 
8, had normal range S100B levels at the time of admission. We assume that these values did not remain at normal levels but proceeded to increase. Investigating the rate of change of serum S100B levels at an individual level would allow the removal of inherent individual variation due to sex or to age—which in this study spans 47–84 yr.
S100B expression is not restricted to neuronal tissues2 and serum S100B levels have been shown to be increased after bone fractures3 or after ischaemia of the liver, gut, or kidney.4 Therefore, S100B may be elevated during sepsis alone, and it may be that the rate of release of serum S100B is higher if there is an underlying encephalopathy, in addition to sepsis. This rate of increase in serum S100B levels may be a more sensitive readout of ongoing pathology, with high rate of increase indicating an underlying brain encephalopathy. In the present study, the average S100B levels seem to be increased at day 7 compared with levels at ICU admission, with a larger spread indicating some patients have lower levels whereas other patients have much higher levels than the average. It would be interesting if this rate of release of S100B was an indicator of prognosis, where if S100B levels are still increasing by day 7, prognosis may be poor and a slight increase or decrease would indicate a better prognosis.
Naples, Italy
* E-mail: orpiazza{at}unina.it
Editor—Drs Panni suggest that S100B changes rather than absolute values may be a better marker of severity of sepsis-associated encephalopathy. They assume that comatose patients who have normal S100B values on ICU admission may proceed to higher values later. As previously described,1 our sepsis patients showed alteration of consciousness at admission; they did not develop it during their ICU stay. In our experience, S100B was measured at ICU admission and after 3 and 7 days: there was not any correlation with neurological outcome at any time point. Any prognostic marker should be precocious and specific: we respectfully disagree with Drs Panni when they suggest that the rate of S100B increase after 7 days of coma may add useful information in prognosis formulation but we support the hypothesis that S100B serum levels measured by commercial ELISA kit do not allow the observers to distinguish brain S100B release from peripheral tissues production.5
References
1 Piazza O, Russo E, Cotena S, Esposito G, Tufano R. Elevated S100B levels do not correlate with the severity of encephalopathy during sepsis. Br J Anaesth (2007) 99:518–21.
2 Haimoto H, Hosoda S, Kato K. Differential distribution of immunoreactive S100-alpha and S100-beta proteins in normal nonnervous human tissues. Lab Invest (1987) 57:489–98.[Web of Science][Medline]
3 Undén J, Bellner J, Eneroth M, Alling C, Ingebrigtsen T, Romner B. Raised serum S100B levels after acute bone fractures without cerebral injury. J Trauma (2005) 58:59–61.[Web of Science][Medline]
4 Pelinka LE, Harada N, Szalay L, Jafarmadar M, Redl H, Bahrami S. Release of S100B differs during ischemia and reperfusion of the liver, the gut, and the kidney in rats. Shock (2004) 21:72–6.[CrossRef][Web of Science][Medline]
5 Piazza O, Cotena S, Esposito G, De Robertis E, Tufano R. S100B is a sensitive but not specific prognostic index in comatose patients after cardiac arrest. Minerva Chir (2005) 60:477–80.[Medline]
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