Looking back, looking forward: key messages 2005 – 2011

In this report

• Laboratory testing
• Prescribing

In this report

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.

Prescribing

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

Notes

• 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

CRP

• "CRP vs ESR Assessing & Measuring the Inflammatory Response" bpac^nz (Jul, 2005).
• “CRP ESR & Thyroid function testing” bpac^nz Report (Oct, 2009).
• “Should I still use both CRP and ESR when investigating temporal arteritis?” Best Tests (Mar, 2011).
• Colombet I, Pouchet J, Kronz V, et al. Agreement between erythrocyte sedimentation rate and c-reactive protein in hospital practice. Am J Med 2010;123(9):863.e7-13.

Iron

• “Tiredness”, Best Tests (Mar, 2006).
• “The laboratory investigation of tiredness”, bpac^nz (Feb, 2006).
• Pasricha SS, Flecknoe-Brown SC, Allen KJ et al. Diagnosis and management of iron deficiency anaemia: a clinical update. MJA 2010;193(9):525-32.

Tricyclic antidepressants

• “Assessment and management of Depression in Older Adults” bpac^nz (July 2011).
• “Depression in elderly people” BPJ 11 (Feb, 2008).

Amoxicillin clavulanate

• “Appropriate use of amoxicillin clavulanate” BPJ 38 (Sep, 2011).
• “Antimicrobials: choices for common infections” Handbook, bpac^nz (Apr, 2011).