In order to bring a medical malpractice claim you typically have to show that the doctor breached the prevailing professional standard of care and that the breach caused injury to you. Given how expensive medical malpractice cases are to prosecute only cases with significant injuries make it to suit as it often would cost more to pursue the case than the potential recovery. If you have been significantly injured you should retain an experienced medical malpractice attorney in your area. If you have not been injured you can still report your doctor to your state's board of medicine. Good luck to you.
I am not clear what you wish to sue for. It may be malpractice if the standard of care requires the results to be relayed sooner and perhaps with some system to assure you received the results. The more important question is whether or not you were injured as a result of the couple day delay. Even assuming arguendo that it is malpractice you would need to prove damages. Hopefully for you you were not damaged and should seek a different physician. If indeed you learn that the delay was detrimental to you you should contact an attorney.
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