As FD says.
The decision to prescribe antibiotics, is rarely based on "science" as such. There is a move for "near patient testing," but it seems to have hit a bit of a brick wall here in the UK. Generally lab tests are problematic, as there are many "senstivity" and "specificity" issues.
In the case of tonsillitis, it's likely (in the UK), that FeverVIEW(?) , Centor or something simillar will be used to reach the diagnosis.....which is basically and algorythm.
In terms of recovery, empirical tests aren't that helpful usually, the AME would be more interested in how you are feeling, rather than your white cell count, I should imagine.