A study of the value of resin-embedded semi-thin sections and electron microscopy in the diagnosis of renal biopsies.

Two hundred consecutive renal biopsies originally studied by light microscopy of paraffin- and semi-thin sections and electron microscopy were reviewed and re-classified according to the proposed WHO classification for glomerular disease. The accuracy of diagnoses based on paraffin sections alone, and of those based on paraffin- and semi-thin sections were compared with the results of the final evaluation, when electron microscopy also was taken into account. Paraffin material showed a diagnostic accuracy of 59 per cent for glomerulonephritis, and 82 per cent for other renal diseases. The diagnostic accuracy of semi-thin sections was 61 per cent for glomerulonephritis and 76 per cent for other renal diseases; i.e. not improved. It is concluded that the study of semi-thin sections cannot replace electron microscopy in the diagnoses of renal biopsies. In the present study, electron microscopy altered the diagnoses in 34 per cent and yielded additional useful information in another 45 per cent of patients with glomerulonephritis. Therefore, the electron microscope should be employed routinely in the study of renal biopsies from this group of patients.