Diagnosis of TBMN
| Characteristic Feature | Sensitivity | Specificity | Comments |
|---|---|---|---|
| Persistent glomerular hematuria, minimal proteinuria, normal BP, and normal renal function | High (80%) | Moderate | TBMN is the most common cause; occurs in IgA disease too but often with higher urinary red blood cell counts and (less commonly) proteinuria |
| Family history of hematuria | Moderate (70%) | High | Family history of hematuria is also common in X-linked Alport syndrome |
| Generally thinned GBM without focal lamellation | 95% | High | |
| Collagen IV α3α4α5 network present in GBM | 100% | Moderate | Supports but does not prove the diagnosis of TBMN |
| α5(IV) collagen chain present in skin | Supports but does not prove the diagnosis of TBMN | ||
| Hematuria segregates with COL4A3/COL4A4 | 40% | High | |
| Hematuria does not segregate with the COL4A5 locus | High | High | Linkage studies require careful characterization of other family members but are possible with very few members |
| Single mutation in COL4A3 or COL4A4 | 80% | Very high |