Diagnosis of the wrong subtype of a disease is a partial misdiagnosis. Doctors sometimes get the basic disease right but either misdiagnose the subtype or simply do not determine the subtype at all.
In many cases, the correct diagnosis of the subtype is very important. For example, the correct diagnosis of diabetes as either Type 1 diabetes and Type 2 diabetes is important to choose between treatment options such as diet, pills, and insulin. And naturally, if you have heart disease it is very important to determine exactly what type you have and what is the exact cause.
Not all subtypes need to be determined. For example, there are dozens of different subtypes of the common cold, caused by a variety of different viruses such as adenoviruses and enteroviruses. However, it is rarely important to determine the exact subtype and most doctors do not try to do so, and would need specialized tests if they had to separate them. This is all unnecessary because the treatment of a common cold is largely unchanged regardless of exactly which subtype is present.
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