1st-order laboratory parameters-obligatory laboratory tests.
- Calcium* [n/↓]
- Phosphate* [n/↓]
- Alkaline phosphatase (AP)* [↑] – typical in osteomalacia, but not specific DD bone metastases.
- Parathyroid hormone (PTH)* [↑- ↑↑]
- 25-hydroxyvitamin D (25(OH)-vitamin D3 ; 25-OH-D3), plasma [↓-↓↓]
- 1,25-(OH)2-vitamin D (1,25-OH-D3), plasma [n-↑]Note: 1,25(OH)2-vitamin D3 levels ↓ + normal 25(OH)-vitamin D3 → synthesis disorder of vitamin D3.
- Histological examination of a bone biopsy/bone punch (generous indication).
* Critical laboratory parameters for follow-up.
Laboratory parameters 2nd order – depending on the results of the history, physical examination and the obligatory laboratory parameters – for differential diagnostic clarification.
- CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
- Differential blood count
- Alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gamma-GT, GGT), alkaline phosphatase, bilirubin.
- Blood gas analysis (BGA)
- [Blood pH: ↑: metabolic or respiratory alkalosis.
- Blood pH: ↓: (metabolic) acidosis, e.g., as a cause of hypophosphatemia or as part of Fanconi syndrome]
- Urine diagnostics
- Urine status and serum glucose [glucose in urine (glucosuria) with normal serum glucose → e.g., Fanconi syndrome; alkaline urine → e.g., renal tubular partial disorder].
- Urinary alpha-1 microglobulin (marker for tubular proteinuria; restriction of tubular reabsorptive function) [tubular damage e.g. as part of Fanconi syndrome or in nephritides, nephropathies, renal involvement].
- Urea, creatinine, if necessary cystatin C or creatinine clearance [creatinine clearance: differential diagnosis renal osteopathy].
- Gamma-glutamyl transferase (GGT) – for differential diagnosis of hepatic AP elevation, indication of celiac disease or alcohol abuse (risk of falls), hepatic osteodystrophy.
- Wg. hypophosphatemia [decrease in blood phosphate level <0.8 mmol/l]
- Phosphate clearance [In hypophosphatemic form of osteomalacia: ↑ ]
- Fibroblast growth factor 23 (FGF23 – in hypophosphatemic form of osteomalacia: to exclude an FGF23-producing tumor[If positive: octreotide scintigraphy or positron emission tomography-computed tomography (PET-CT)]
- Serum protein electrophoresis, immunofixation in serum and urine – for differential diagnosis of monoclonal gammopathy or hypogammaglobulinemia as evidence of monoclonal gammopathy of unclear significance (MGUS) or plasmacytoma (multiple myeloma) or systemic inflammatory disease.
Disease or cause | Ca | Phosphate | AP | PTH | 25-OH-D3 | 1,25-OH-D3 |
Vitamin D deficiency + decreased 25-hydroxylation. | ↓ | ↓ | ↑↑ | ↑-↑↑ | ↓ | N-(↑) and (↓), respectively. |
Decreased 1α-hydroxylation: vitamin D-dependent rickets type I (VDDR-1). | ↓ | ↓ | ↑↑ | ↑ | N-↓ | ↓↓ |
Decreased 1α-hydroxylation: renal insufficiency. | ↓ | ↑ | ↑-↑↑ | ↑-↑↑ | N | ↓ |
Hypophosphatemia | N | ↓↓ | ↑↑ | N | N | N-↓ |
Mineralization defect: hypophosphatasia (synonyms: Rathbun syndrome, phosphatase deficiency rickets). | N | N | ↓-↓↓ | ↓-u.N. | N | N |
Target organ resistance:vitamin D-dependent rickets type II (VDDR-2). | ↓-↓↓ | ↓ | ↑↑ | ↑ | N-↓ | ↑-N |