Objective To investigate the feasibility of using Cariostat test for caries risk assessment in adult outpatients and provide a reference basis for caries prevention and treatment in adult outpatients of different ages.Methods Fifty-two adult patients of different ages(18-24,25-34,35-44,45-54,and≥55 years old)attending outpatient clinics of The Affiliated Stomatological Hospital of Nanjing Medical University were tested for caries activity using the Cariostat test.Oral examinations were conducted according to the criteria of the 5th edition of the Basic Methods of Oral Health Surveys of the World Health Organization,and on-site questionnaire sur-veys were performed for the Cariogram assessment system.Oral examinations included assessments of dental arch conditions and caries status,while questionnaire surveys covered dietary habits,oral health care habits,etc.The caries status of adult outpatients of different age groups was analyzed,and caries activity was assessed using the Cariostat test.The caries risk levels were determined,and the con-sistency between the Cariostat test and the Cariogram assessment system was evaluated.Results It was found that there was a differ-ence in mean decayed,missing and filled surfaces(DMFS)between the low-risk group of adult outpatients with different caries risk levels classed by the Cariostat test and the intermediate and high-risk groups(P＜0.05).There was a difference in mean decayed,missing and filled teeth(DMFT)and mean DMFS between the low-risk group of adult outpatients with different caries risk levels classed by Cariogram and the intermediate and high-risk groups(P＜0.05).The evaluation results of caries risk levels in adult outpa-tients classed by the Cariostat test and the Cariogram assessment system showed a Kappa value of 0.467(P＜0.05)in the≥55 years old group,indicating moderate consistency.Conclusion The Cariostat test is useful in understanding the caries activity of adult outpa-tients and is particularly accurate and effective in patients at the age of 55 or older.