The detection rates of AKI in local hospitals from regions of different economic levels
Between January and July 2013, a total of 116,788 patients were admitted to the 22 local hospitals included in our study. 1,942 patients were identified as AKI using the expanded criteria, corresponding to a detection rate of 1.66%, including 790 cases (0.68%) that were identified by the KDIGO criteria. These regions were divided into three groups by tertiles according to pcGDP levels: pcGDP Tertile 1 (underdeveloped regions), pcGDP Tertile 2 (moderately devoloped regions), and pcGDP Tertile 3 (developed regions). A comparison of detection rates among the three pcGDP groups showed that the detection rate for AKI in the pcGDP Tertile 1 group was the lowest (0.49% and 1.24% according to the KDIGO and expanded criteria, respectively). We also found that the recognition rates for AKI (including timely-recognition and delayed recognition) in the pcGDP Tertile1 and pcGDP Tertile 2 groups were significantly lower than that in the pcGDP Tertile 3 group (26.38% and 24.32% vs 32.98%, P = 0.001, respectively). There were also significant differences in the detection rate for AKI when compared between different regions with different economic levels, as shown in Table 1.
Characteristics of patients with AKI in local hospitals from regions of different economic levels
The age of the 1,942 AKI patients identified in local hospitals was 64.0 ± 17.2 years, with more elder patients in developed areas. Male patients were the majority of AKI cases in all regrions. Of the 1,942 AKI patients, 1,070 (55.1%) cases were classified as having pre-renal AKI, 468 (24.1%) cases as intrinsic-renal AKI, 198 (10.2%) cases as post-renal AKI, and the remaining 206 (10.6%) patients could not be clearly classified. With the exception of intrinsic-renal AKI, there were significant differences in the proportion of other AKI classifications across the different pcGDP groups (thus representing differences in accordance to economic level) (Table 2). The most common causes that might contribute to the development of AKI were low renal perfusion (78.0%), drug factors (69.9%), and other critical illness (38.1%). Compared with moderately developed regions and developed regions, the proportion of AKI cases caused by nephrotoxic drugs was the lowest in underdeveloped regions (59.7% vs 72.7% vs 72.7%, P < 0.001) (Table 2).
Patients in local hospitals from underdeveloped regions had the highest proportion of patients with unclassified AKI (12.9% vs 11.5% vs 7.4%, P = 0.010) or reaching AKI stage 3 (37.9% vs 25.1% vs 25.7%, P < 0.001) compared to patients from moderately developed or devleoped regions. Compared with underdeveloped regions and developed regions, the proportion of AKI cases of referral to nephrology providers was the lowest in moderately developed (16.9% vs 22.3% vs 22.8%, P = 0.007). There was no difference in the proportion of patients in ICU, with indicators for RRT, or receiving RRT treatment, when compared among different pcGDP tertile groups. The proportion of patients who had not been recognized with AKI on time (including non-recognition and delayed recognition) was higher in local hospitals from underdeveloped and moderately developed regions than that in developed regions (P < 0.001). Local hospitals in underdeveloped regions had the highest proportion of patients with unrecovered renal function (34.4% vs 29.4% vs 31.6%, P = 0.04) and the highest mortality rate (15.5% vs 10.3% vs 7.0%, P < 0.001) compared to those from moderately developed or devleoped regions. There was no significant difference in the duration of hospital stays or treatment costs of AKI patients when compared among local hospitals from different economic levels (Table 2).
The characteristics of AKI patients in local hospitals from different geographic regions
The frequency of AKI patients in South China and Southwest China was noticeably higher than those in other geographic regions, regardless of whether the diagnoses were based on KDIGO criteria, expanded criteria, AKI recognition rate, or nephrology referral. When analyzing the classification of AKI, we found that pre-renal AKI was more common in the Western regions (including the Southwest and Northwest; 63.9% and 62.5%, respectively) than that in North (56.5%) and South (51.5%) regions (P < 0.001). Etiological analysis showed that injury factors other than renal hypoperfusion to the kidneys differed significantly across different geographic regions. Northwest and Southwest regions had higher proportion of patients with potential nephrotoxic drugs use (75.0% and 76.3%, respectively). The Southwest region had the most patients with environmental toxin-induced AKI compared to other regions (10.0% vs 0.0%~1.9%, P < 0.001). AKI caused by sepsis or surgical factors was more common in South China. The underlying diseases also varied across different geographic regions. AKI patients with diabetes, cardiovascular disease, and cerebrovascular disease, were more frequently found in North China. Northwest China had the highest proportion of AKI patients with hypertension. AKI patients with basic chronic kidney disease and malignancies were most common in South China (Table 3).
Risk factors affecting in-hospital mortality of AKI patients in local hospitals
Altogether 1,913 patients with AKI had information on mortality during hospitalization, and the rate of all-cause in-hospital mortality was 10.5% (200/1,913). In the univariate analysis, age, sex, geographic region, pcGDP, AKI classification, injury factors, AKI stage, delayed recognition, staying in ICU, indication for RRT, RRT rate, comorbidity of CEVD and malignancy were associated with the outcome (all P values < 0.05). We included the above variables in the multivariable analysis and found that age, sex, geographic region, staying in ICU, AKI stage, injury factors, recognition of AKI and pcGDP levels were still associated with the outcome (all P values < 0.05). Among them, advanced age (≥ 80 versus 18–39, OR = 2.34, 95%CI: 1.21–4.56), male gender (versus female, OR = 1.60, 95%CI: 1.10–2.33), staying in ICU (OR = 1.61, 95%CI: 1.08–2.40), higher AKI stages (stage 2 versus stage 1, OR = 1.79, 95%CI: 1.13–2.83; stage 3 versus stage 1, OR = 3.59, 95%CI: 2.28–5.67), using nephrotoxic drugs (OR = 2.02, 95%CI: 1.28–3.20), being with other critical illness (OR = 6.31, 95%CI: 3.93–10.15) and delayed recognition (versus timely recognition, OR = 2.77, 95%CI: 1.47–5.22) were associated with increased in-hospital mortality, while in hospitals from South China (OR = 0.43, 95%CI: 0.27–0.71) or from regions with the highest pcGDP levels (tertile 3 versus tertile 1, OR = 0.44, 95%CI: 0.25–0.78) were associated with decreased in-hospital mortality (Table 4).