Abstract: Objective To investigate the correlation between absolute value of serum lactic dehydrogenase(SLDH) and CT quantitative score of exudative lesion of Pneumocystis Jiroveci pneumonia(PJP) complicating AIDS and to evaluate the clinical value of the CT quantitative scoring in severity assessment and the outcome prediction. Methods A total of 88 cases suffering from AIDS complicated by PJP were selected from 142 patients and their chest CT scans were retrospectively analyzed. The CT quantitative scores were obtained based on the extent and density of the exudative lesion. Their correlation with the in-sync absolute value of SLDH was statistically analyzed. Furthermore, the 88 cases were divided into non-respiratory failure group(Group A) and respiratory failure group(Group B) based on their outcome. The beween groups difference analysis was conducted in terms of CT quantitative scores and corresponding SLDH. The threshold value was predicted by ROC analysis. Results Significant positive correlations between the extent, density and CT quantitative scores of the exudative lesion and the in-sync SLDH were shown(P<; 0.01), with coefficients of 0.59, 0.68 and 0.79, respectively; Significant differences were shown in terms of each CT quantitative score and in-sync absolute value of SLDH between Group A and B, with data of Group A being significantly lower than those of Group B (P<; 0.05); The CT quantitative scores were proved to be the most accurate predictor for respiratory failure, with a Youden index of 0.81, the area under the curve(AUC) of 0.95 and the prediction threshold of 79.9. Conclusion The CT quantitative scores of exudative lesion of PJP complicating AIDS can provide Objective , accurate and reliable data for early assessment of severity and the outcome prediction, which has significant value in clinical practice.

Key words: AIDS, Pneumocystis jiroveci（PJ）, Pneumocystis jiroveci pneumonia（PJP）, CT, Lactate Dehydrogenase（LDH）