Table 2

Addtional blood tests: responding to results

Elevated ESR/CRP
  • Consider the following possibilities:

    •  –Infection.

    •  –Inflammation (including IBD).

    •  –Recurrent malignancy.

    •  –Non-GI causes (eg, rheumatoid arthritis, vasculitis, connective tissue disorders).

RBC folate deficiency
  • Consider referral to dietitian for dietetic advice/supplementation.

  • Check coeliac screen.

Iron deficiency: ferritin, % transferrin saturation, red cell indices
  • If iron is low and iron saturation is low, discuss with supervising clinician and oncology team within 2 weeks.

  • If intolerant of oral iron: consider intravenous iron infusion.

If excess iron=raised ferritin with transferrin saturation>45%
  • Consider haemochromatosis: Discuss with supervising clinician and consider genetic testing.

Low vitamin B12
  • Exclude the possibility of inadequate dietary intake (especially vegans)—if this is the probable cause, consider trial of oral vitamin B12 supplements. Dietetic referral.

  • Consider possibility of pernicious anaemia—check parietal cell and intrinsic factor antibodies.

  • Exclude SIBO (p. 27). Recheck result after treatment with antibiotics.

  • Check coeliac screen.

  • If confirmed on repeat testing and not treatable with oral replacement, eg, after gastrectomy, ask GP to arrange lifelong intramuscular replacement.

  • Metformin therapy.

Abnormal thyroid function tests
  • If TSH suppressed (<0.5 mIU/L), recheck result with thyroid auto antibodies.

  • If TSH suppression confirmed, request GP to organise/refer for radiological imaging and treatment.

  • If TSH elevated (>4.0 mIU/L), recheck result. Also check 09:00 cortisol if Na ≤135 mmol/ L and K+ >4 mmol/L or raised urea or creatinine.

  • If TSH elevation confirmed: start thyroid replacement medication. Request GP to monitor long-term. Review bowel function after 6–8 weeks.

Abnormal coeliac serology
  • If IgA deficient, request IgG coeliac screen.

  • If TTG elevated, confirm with SI biopsy.

  • Refer for dietetic advice once diagnosis is confirmed.

  • Refer to coeliac clinic.

Serum Mg2+
  • If <0.3 mmol/L, this is an emergency.

  • Check K+ and Ca2+, if low, will also need replacement.

  • If 0.3–0.5, consider intravenous replacement if symptomatic or fall in Mg2 level has been acute. If oral replacement is given, check for response after 5–7 days with repeat blood tests.

  • If oral replacement is used, Mg Oxide or Mg aspartate provide better bioavailability and cause less diarrhoea than other Mg preparations.

  • If associated with refeeding syndrome, also monitor PO4 and K+ closely and give intravenous vitamin replacement.

  • Ca, calcium; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; GI, gastrointestinal; GP, general practitioner; IBD, inflammatory bowel disease; K, potassium; Mg, magnesium; Na, sodium; PO4, phosphate; RBC, red blood cell; SIBO, small intestinal bacterial overgrowth; TSH, thyroid stimulating hormone; TTG, tissue transglutaminase.