Not necessarily. Medicine is not an exact science; doctors are not required to be right every time they make a diagnosis. It is a fact that a misdiagnosis can be arrived at through standard tests, even when the tests are performed accurately or evaluated by a skilled doctor with the utmost care.
A misdiagnosis may be malpractice if the doctor fails to get a medical history, order the appropriate test for the illness, or recognize the symptoms of the illness. And yet, there is no basis for a malpractice claim if there is no injury, loss or damage as a result of the misdiagnosis and consequent treatment, on the theory that you are no worse off than you were before.