When doctors suspect that something is wrong with a patient, they will order a clinical laboratory tests list based on symptoms described. While it would be nice if the clinical laboratory tests list encompassed all the tests possible, that would require too much blood. Also, it would take up a lot of the clinicians’ time in the lab.
This is why doctors use their own best judgement based on their medical background to choose the tests that will likely be the cause of the ailments.
The tests go by various names, so it can be confusing for someone without a medical background. For example a complete blood count test is called CBC but also can go by the name of hemogram.
It is important for the doctor to ask questions, even of a personal nature, to get the right tests ordered. So even if you find it difficult, always disclose any risky activity you have engaged in, such as multiple sexual partners or intravenous/any illegal drug use.