Is it obligatory for an employee to inform customers about erroneous test results, if the nature of his work is confined to drawing blood and reading results, and it is not his responsibility to issue the results? And what are the consequences if he does not inform them?

You must advise the management to clarify the truth about the test to the people, and that deceiving customers is a betrayal of trust and tampering with people's health, in accordance with the Almighty's saying: "Indeed, Allah does not like traitors," and the Prophet's (peace be upon him) saying: "Whoever deceives is not from me." If they do not comply, you must inform those higher up than them. If they still do not comply, you must inform the person undergoing the analysis of the truth, in accordance with the hadith: "It is not permissible for anyone to sell something except that he clarifies what is in it, and it is not permissible for one who knows that except that he clarifies it," and the requirement to disclose defects to those who are aware of them.