robust data assessing the value of procalcitonin ( pct ) for monitoring treatment response in abdominal sepsis are rare , so the study of jung and colleagues published in the previous issue of critical care is most welcome .
they concluded that a decrease of pct to 0.5  ng / ml lacked sensitivity to predict treatment response and a decrease of at least 80% from its peak failed to accurately predict treatment response .
the value of the study is limited by the small number of patients included , the single - center approach and its observational character . nevertheless , it is to date among the best available evidence we have for these critically ill patients .
international databases show that one in four cases of severe sepsis or septic shock is caused by intra - abdominal infection .
abdominal sepsis is not just a single disease , but comprises a group of different entities .
almost 90% of all intra - abdominal infections are so - called secondary peritonitis and require a primarily surgical approach ( 87% of patients had surgical intervention in the study of jung and colleagues ) .
secondary peritonitis consists of community acquired and postoperative nosocomial forms , the latter one following a previous surgical intervention ( anastomotic insufficiency following anterior rectum resection ) .
tertiary nosocomial peritonitis is a persistent intra - abdominal infection without a surgically treatable focus , but this point is difficult to assess without an uncontributive reoperation proving that the patient indeed has a tertiary peritonitis .
primary inadequate and inappropriate antibiotic regimens for both forms of nosocomial peritonitis are associated with substantially worse prognostic outcome for patients with intra - abdominal infections and result in substantial increases in health care costs .
the difficulties associated with abdominal sepsis are complicated by uncertainty about surgical control of the source of the sepsis .
do we have any reliable parameters that enable us to decide whether to perform a relaparotomy or not ( in the jung and colleagues study about 20 out of 101 patients required a relaparotomy ) ?
an analysis of all investigated markers , including pct , failed to detect specific parameters that can be used under these difficult conditions .
current guidelines recommend administration of broad - spectrum antimicrobials within 1  hour of the diagnosis of severe sepsis or septic shock .
this recommendation is based on the evidence that delaying antimicrobial therapy in patients with sepsis- related hypotension is associated with increased mortality .
pct has been evaluated over recent years as to whether it can be used to detect the presence of different types of infection , treatment failure or adverse outcome .
the promising initial publications reporting the results of using serial serum pct concentrations to guide duration of antibiotic therapy in patients with community - acquired pneumonia   have only partially been confirmed in critically ill patients .
a recent randomized multicenter trial enrolling critically ill patients   with mainly respiratory tract infection showed that duration of antibiotic therapy can be reduced by a mean of 2.7  days without impact on mortality .
but unfortunately , pct had no influence on the duration of antibiotic therapy in patients with intra - abdominal infections .
smaller randomized studies show that significant pct - guided reduction of antibiotic exposure can safely be accomplished in patients with severe sepsis and septic shock and in surgical patients with sepsis .
more recently , it has been suggested that pct may be of value as a prognostic marker .
daily measurements of pct in a general icu population in a recent large multicenter randomized study   were associated with increased use of antibiotics and duration of mechanical ventilation . this commentary has been written by an abdominal surgeon and an intensivist , representing the two disciplines most frequently involved in the treatment of an important subgroup of critically ill patients . in this 
war against the high mortality from abdominal sepsis , surgeons and intensivists are brothers in arms .
the study of jung and colleagues indicates that pct is still a valuable weapon in this war - but far from being the magic bullet .
 the ideal management of infection includes not only the early identification and start of effective therapy but also the correct categorization of non - infected patients in order to avoid unnecessary use of antimicrobials . 
 the availability of a specific and sensitive test for the presence of infection is of paramount importance to improve the prudent use of antimicrobial therapy . 
 procalcitonin ( pct ) has been evaluated over recent years as to whether it can be used to detect the presence of different types of infection , allows reduced duration of antibiotic therapy , or predicts treatment failure or adverse outcome . in the previous issue of critical care , jung and 
 colleagues report about the monitoring of treatment response in abdominal sepsis by repetitive determination of pct . 
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