Differences in institutional treatment protocol for septic DIC
In Japan, medical institutions can be classified into three groups according to their policies on the administration of anti-septic DIC therapies, which generally consist of anti-coagulants such as rh-TM and/or AT concentrates: 1) the NO-TX group: hospitals that typically do not provide anti-coagulation treatment for septic DIC, a policy that is considered valid not simply because infection management is expected to relieve sepsis even in the case of septic multi-organ system failure (MOF) but also because it is in keeping with the Surviving Sepsis Campaign Guidelines (2), 2) the DO-TX group: hospitals that routinely provide anti-coagulation therapies to improve MOF in septic DIC patients, and 3) the DEP-TX group: hospitals that provide such treatments at the discretion of the physician-in-charge, which means that these hospitals occupy an intermediate position between the other two extremes in terms of the rate at which they administer anti-coagulation therapies. In this study, we have clearly shown that differences in institutional policies regarding the administration of anti-coagulation treatments for septic DIC, are associated with differences in in-hospital mortality rate (HMR) and in adjusted HRs of HMR, especially between the DO-TX and NO-TX groups of patients with septic DIC. This finding appears to support the use of anticoagulants such as rh-TM or AT concentrates (12) for septic DIC with MOF.
International differences in in-hospital mortality rates of patients with septic DIC
Septic DIC is a specific pathology resulting from hypercoagulation followed by prolonged anti-fibrinolysis, which leads to multiple organ failure due to impairment of microcirculation related to the formation of microthrombi (1). Treating the initial infection is a requisite step in the treatment of sepsis, and should be done in parallel with other standard therapies including respiratory, hemodynamic, and nutritional management (13). Together, these therapeutic strategies are recommended globally as “bundle therapy for severe sepsis.” Despite a report of improvement in the survival rate among severe sepsis patients after the implementation of bundle therapy (14), the mortality rate among these patients remains less than optimal. As another aspect, the outcomes of sepsis cases can be considerably worsened when disseminated intravascular coagulation occurs (15). Therefore, we need additional therapeutic interventions such as anti-coagulation treatments for severe sepsis with DIC. Such treatments have been administered in Japan, usually in the form of rh-TM and/or AT III concentrates (3, 12), but have not been used in clinical settings in Western countries. Furthermore, interestingly, the use of AT III is even prohibited by the Surviving Sepsis Campaigning Guidelines 2016 (16). North and South America and certain European countries have reported improvements in the mortality rate associated with severe sepsis/septic shock in the past decade (17), yet even their improved mortality rates are markedly worse than those reported in a Japanese Registry Study when mortality is considered according to the number of affected organs (18). The rate of hospital mortality in Western countries remains almost double that in Japan: when one organ is affected, there is a 27% hospital mortality rate in Western countries compared to a 13% rate in Japan; when two organs are affected, the rate is 34% in Western countries and 19% in Japan. Although we should be very cautious in any comparison of mortality rates between two different populations, since there are several potential confounders, such as differences in medical insurance systems among the various countries, it is important to be aware that there are dramatic differences in mortality between countries with therapeutic interventions such as anti-coagulation therapy for septic DIC and countries without.
Protocol-related differences in in-hospital mortality rates of patients with septic DIC within Japan
As we have mentioned, international comparisons of mortality rates can be problematic due to differences between the populations and healthcare systems involved. The impact of population-related confounders can be reduced, and more meaningful comparisons can be obtained, by comparing mortality rates among hospitals that are within the same country but that operate according to different treatment protocols. The fact that some institutions in Japan perform anti-coagulation treatments while others do not has enabled us to evaluate the effects of anti-coagulation treatments in patients with septic DIC in the clinical setting (3, 4). In the present study, we have clearly demonstrated that anti-coagulation therapy for septic DIC patients is associated with reduced in-hospital mortality rates as compared with no such treatments.
Limitations of the present study
Patient characteristics and sample size
This study incorporated data obtained from only 40 institutions in Japan, most of which were critical care centers or university hospitals, and the data from such institutions may not be representative of the entire country. Furthermore, the severity of sepsis in patients admitted to such hospitals may be greater than that in patients admitted to local or regional medical centers; in fact, as Table 1 shows, the proportion of patients with APACHE II score greater than 20, indicating a rather severe disease state, was 64.3% in the present study. Within this patient population, however, we found a significant reduction in in-hospital mortality rate at hospitals that routinely provided anti-coagulation treatments to septic DIC patients.
The total number of patients including non-DIC patients with complete information on both the JAAM criteria and the ISTH criteria was 2513, which we believe is sufficiently large for an analysis of the association between institutional anti-coagulation therapy protocols and in-hospital mortality. Furthermore, the variety of institutional criteria for anti-coagulation therapy in Japan, regardless of whether therapy for septic DIC is provided, may improve our ability to evaluate its treatment effect on this type of DIC.
If compared with patients who were excluded because of incomplete data for score calculation for JAAM and ISTH, such excluded patients were more likely to be younger, have more SOFA score changing by ≥ 2, and higher APACHE II scores.
Rate of anti-coagulation therapy administration in each group
Table 2 shows the rate at which anti-coagulation therapy was administered in each group. The differences in this rate among the three groups (NO-TX, DO-TX and DEP-TX) were dramatic: in JAAM-DIC patients, anti-coagulation treatment was given to 10.6% of patients in NO-TX hospitals, 73.4% of patients in DO-TX hospitals, and 54.3% of patients in DEP-TX hospitals. Even in NO-TX hospitals, a small percentage of DIC cases were treated with anti-coagulation therapy. Hospitals were classified into the NO-TX group if they self-reported that they did not typically provide anti-coagulation therapy. This classification method could be the most serious limitation of this study. Although the observed huge differences in the proportions of patients who received DIC treatment in each group seem to confirm the validity of the three groups in this study, we need to perform a future RCT study to define effects of institutional anti-coagulation protocol on intra-hospital mortality in septic DIC patients.
Which criteria for septic DIC: JAAM or ISTH?
In this study, septic DIC patients diagnosed according to the JAAM criteria were also assessed by the ISTH criteria for overt DIC. The JAAM criteria are well established and show very high sensitivity and specificity in diagnosing septic DIC (19, 20, 21). In general, the ISTH criteria are used to determine overt DIC, while the JAAM criteria are used to diagnose DIC at an earlier, less easily detectable stage. Therefore, ISTH-DIC patients usually have more severe sepsis than JAAM-DIC patients do. In fact, in a validation study of the JAAM-DIC criteria, ISTH-DIC patients have been reported to have more severe sepsis (19). Furthermore, the ISTH-DIC patients in this study were more likely to have more severe APACHE II scores greater than or equal to 30 (data not shown). As we (12) and others (3, 22) have reported previously, anti-coagulation therapy could be more effective for septic DIC patients with higher severity, such as the ISTH-DIC patients in this study. However, as the lower panel of Table 3 shows, when only ISTH-DIC patients were considered, there were no statistically significant differences in in-hospital mortality rate among the three treatment-protocol groups. Possible explanations for this include the limited number of ISTH-DIC cases after patients with incomplete descriptions of the laboratory data needed to calculate ISTH scores were excluded, as well as the possibility of other unknown confounding factors. Nevertheless, as Table 4 shows, we demonstrated clearly that, among ISTH-DIC patients, adjusted HRs of in-hospital mortality were significantly lower in the DO-TX and DEP-TX groups than in the NO-TX group. This matter will need to be clarified in the future.