Objective To investigate the early diagnostic value of single or combined measurement of serum procalcitonin( PCT),peripheral white blood cells( WBC),and ratio of WBC to platelets( PLT)( WBC / PLT) for spontaneous bacterial peritonitis( SBP) in patients with liver cirrhosis. Methods The clinical data of 129 patients with liver cirrhosis who were admitted to our hospital from January 2011 to June2013 were retrospectively analyzed. One hundred and twelve patients who died of liver cirrhosis were divided into infection group,in which the cause of death was complicated infection( n = 94,including 61 SBP cases),and non- infection group( n = 18). Seventeen patients with compensated cirrhosis were assigned to control group. Before treatment with antibiotics,routine bacterial culture was made,and serum PCT,WBC,and WBC / PLT were measured. Mean comparison was made by t test and chi- square analysis. Ratio comparison was made by Pearson χ2test. The receiver operating characteristic( ROC) curve was plotted to calculate the sensitivity and specificity. Results There were 66 patients in the infection group whose bacterial culture was positive,and the positive rates for cultures from blood,ascites and other exudates were 25. 8%,30. 3%,and 43. 9%,respectively. In the infection group,lung infection,SBP,and unknown focus of infection accounted for 8. 5%,64. 9%,and 26. 6% of total cases,respectively. The level of serum PCT in the infection group was significantly higher than those in the non- infection group and the control group( F = 10. 98,P < 0. 05),but showed no significant difference in patients with different sites of infection. When PCT was ≥0. 5 ng / ml,the sensitivity and specificity for diagnosis of complicated infection were 92. 5%and 77. 1%,respectively,and the area under the ROC curve was 0. 89. When PCT was ≥2 ng / ml,the sensitivity was 62. 7% and the specificity was 94. 2%. When the peripheral WBC count was ≥10 × 109/ L and the WBC / PLT was ≥0. 25,the sensitivity was 47. 8% and39. 6%,respectively,and the specificity was 100%. When PCT was combined with WBC / PLT for diagnosis of complicated infection,the sensitivity was 76. 8% and the specificity was 94. 2%. For patients with SBP,the levels of PCT and WBC and WBC / PLT showed no significant differences between positive and negative ascites cultures. When PCT was combined with WBC / PLT for diagnosis of SBP,the sensitivity was 83. 6% and the specificity was 94. 2%. Conclusion PCT and WBC / PLT can be used as early diagnostic indicators for complicated infection in cirrhotic patients. PCT combined with WBC / PLT has a significant value for early diagnosis of SBP in cirrhotic patients.