NEW DELHI: "There is nothing wrong if knowledge of a professional is tested", the Supreme Court observed on Friday when three Chattisgarh-based doctors came to it saying they are being forced to undertake the test to continue practising as ultrasonologists.Observing that the test of professional skill was not wrong and would ultimately benefit patients, the top court said however that the senior MBBS doctors, who have been performing ultrasonography for 15 years or more, can be allowed to practice if they do not wish to take up the test now prescribed by the authorities."Even lawyers are asked to take examination to practice law. We see no wrong if the knowledge of professional is tested," said the bench headed by Chief Justice S A Bobde."But, we can protect those who have been practising as ultrasonologist for a period of 15 years or more," said the bench, which also comprised Justices B R Gavai and Sury Kant.The bench asked as to what was wrong if the patients are treated by qualified professionals and gave the example of robotic surgery and said that many old physicians were not equipped to deal with the aspect of medical science.Senior advocate Mukul Rohatgi , appearing for the doctors Anil Wasti, Manjeet Singh Chandrasen and Bhaskar Prasad, said that 2014 Rules have been made effective with retrospective effect and mandated that the practising doctors will also have to take the exam."Any rule cannot be made effective with retrospective effect," he said, asked as to how doctors of 20 years of experience be asked to take up the test.Moreover, the apex court is already examining the validity of certain provisions of the the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994 and rules made under it, he said.Rohatgi said even lawyers are supposed to take up the All India Bar Examination to practice law, but it cannot be made effective with retrospective effect and senior lawyers like him cannot be made to take up the test.The court agreed with the submission and said that his clients can keep practising as ultrasonologists even if they do not take up tests.Earlier, the top court had issued notice on various pleas including the one flied by the Centre challenging the decision of the Delhi High Court removing the mandatory six-month training earlier required to perform ultrasonography.The Centre had said that there was a need to revisit the issue in the wake of the Delhi High Court verdict.Besides the Centre, Indian Radiological and Imaging Association, the association of radiologists in the country, had moved the apex court challenging the High Courts decision on the issue.The high court had declared the Rule 3(3)(1)(b) framed under the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994 as ultra vires.It had done away with the mandatory six months training which was earlier required to be able to perform an ultrasound under the ambit of the law.