Bone Scans

Investigations

Biochemical Tests

• Serum Calcium & Phosphate
• Serum Alkaline Phosphatase (ALP):
  • Measures osteoclastic activity
  • Indicates bone turnover rate
• Vitamin D levels
• Urine Calcium & Phosphate excretion
• Renal profile
• Liver function tests

Imaging Studies

• X-rays
• DEXA scans (discussed below)

DEXA Scan

Overview

• Bone Mineral Density (BMD) measurement
• DEXA: Dual Energy X-ray Absorptiometry
• Primary sites: Spine / neck of femur
• Screening sites (Ultrasound): Foot / wrist

WHO Classification of BMD Using DEXA Scan

Reference: L2-L4 vertebrae

Category	T-Score	Description
Normal	$\ge -1$	Within 1 SD of young adult mean
Osteopenia	-1 to -2.5	Between 1-2.5 SD below young adult mean
Osteoporosis	$<-2.5$	More than 2.5 SD below young adult mean
Severe Osteoporosis	$<-2.5$ + fracture	Osteoporosis with history of fracture

Note: T-score represents the number of standard deviations (SD) a patient is above or below the mean BMD of a young adult.