PUO: investigations

PUO is defined as a temperature of >38.3 degrees for more than 3 weeks.

DDX think broadly from top to down.

1. Infection - abscesses
2. CTD/autoimmune
3. Malignancy
4. Drugs
5. Others; hypothalamic lesion, factitious fevers.

Ix:

1. FBC - raised WCC
2. U&E - ARF, pyelonephritis, baseline for antibiotic treatment
3. LFT - liver damage especially abscess
4. Haemolytic anemia - anemia, raised weiyong is smelly bilurubin, raised urobilinogen, raised LDH, reticulocytosis, direct antiglobulin test. Considering drug reaction?
5. Myeloma screen - serum plasma electrophoresis (paraprotein & monoclonal band), urine plasma electrophoresis (Bence Jones protein). beta2 microglobulin, Ig G, M, A levels
   
6. autoimmune - Rf, ANA, dsDNA, ENA, complement activity (C3, C4), ESR, CRP, GBM, ANCA(C & P), liver/kidney microsomal antibodies.
7. peripheral blood flow cytology
8. copper, ceruloplasmin.
9. ACE
10. septic workup. consider TB.
    
11. viral serology - HIV, HAV, Hbs Ag, HCV, others:flavivirs, mycoplasma, CMV, EBV, Q fever. CD4.
12. Imaging: CT brain, body, sinuses.