What investigations are recommended to rule out other conditions when suspecting Polymyalgia Rheumatica?

When suspecting polymyalgia rheumatica (PMR), investigations to exclude other conditions include blood tests such as full blood count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) to assess inflammation levels, as these are typically elevated in PMR but can also indicate other diseases. Additionally, baseline urea and electrolytes, liver function tests, calcium, and HbA1c should be checked to exclude other causes and assess for comorbidities. Serum protein electrophoresis and urine Bence–Jones protein or serum-free light chains may be indicated if ESR is disproportionately elevated compared to CRP to exclude plasma cell disorders. Screening for infections (urine dipstick, chest X-ray, latent tuberculosis tests) and osteoporosis risk (thyroid stimulating hormone, vitamin D, bone density tests) may also be appropriate depending on clinical context. These investigations help differentiate PMR from conditions such as giant cell arteritis, infections, malignancies, and other inflammatory or metabolic disorders.