In this report
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Laboratory testing

Appropriate use of CRP and ESR

  • CRP should be chosen first on most occasions
  • Simultaneous testing of CRP and ESR is rarely indicated
National testing average per GP  

In July 2005, bpacnz published guidance on the appropriate use of CRP and ESR. CRP is now more frequently requested than ESR and simultaneous testing of CRP and ESR has decreased considerably. It is now well accepted that on most occasions, CRP should be the sole test of inflammation. CRP provides a more accurate measure of the acute phase response because:

  • CRP is a direct, rapid measure of the inflammatory process, whereas ESR is an indirect measure and may be affected by many other conditions and therefore give misleading results.
  • There are distinct normal and abnormal reference ranges for CRP that do not vary with age or gender.

Investigating iron deficiency

  • Ferritin should be used to investigate suspected iron deficiency.
National testing average per GP  

Serum ferritin alone is a highly sensitive test of iron deficiency in patients with otherwise good health. Full iron studies (including serum iron and transferrin/saturation) do not increase the sensitivity of ferritin. However full iron studies may be indicated if iron overload is suspected, or other comorbidities are known or suspected. If serum ferritin is increased, iron studies may be requested for further investigation.


Choosing a tricyclic antidepressant for older adults

  • Use nortriptyline if a tricyclic antidepressant is indicated for older adults.
National prescribing average per GP  

Tricyclic antidepressants (TCAs) are most commonly used in the treatment of depression (second-line after selective serotonin reuptake inhibitors) and in the treatment of neuropathic pain (generally in low dose). If a TCA is indicated, nortriptyline is the preferred choice in older adults because. Compared to other TCAs such as amitriptyline, dothiepin and doxepin, it is less likely to cause sedation, hypotension or anticholinergic effects, e.g. dry mouth, constipation and cognitive impairment.

Appropriate use of amoxicillin clavulanate

  • Use amoxicillin clavulanate for only a few selected indications
National prescribing average per GP  

Ideally broad-spectrum antibiotics, such as amoxicillin clavulanate, should not be used when another narrower-spectrum antibiotic could be prescribed. Amoxicillin clavulanate is indicated as first line empirical treatment for the following infections only:

  • Animal and human bites
  • Diabetic foot infections
  • Periorbital/facial cellulitis


  • The data in this report was sourced from the NZHIS Pharms and Labs data warehouses for the calendar years specified.
  • Some numbers may be affected by rounding.

Further reading



Tricyclic antidepressants

Amoxicillin clavulanate