Yes, it is valid. According to the information brochure, https://bceceboard.bihar.gov.in/pdf_Pros/PROS_UGMAC20.pdf,  the PWD certificate can be issued by a Competent authority at State level. But it is mandatory that you should visit one of the Disability assessment centers if you want to claim PWD reservation in All India Counselling. Under All India Quota, All the 15% of All India Quota Seats except for Jammu and Kashmir, 100% Seats at Deemed and Central Universities, IP Quota seats in ESIC Colleges, Seats at AFMC, AIIMS and JIPMER are filled by DGHS. For claiming PWD reservation in any of these, you need to visit the Disability Assessment Center.