Dr Anna Luo

Background

Psoriasis is a common inflammatory condition that affects people of all ages and ethnicities. It is associated with a number of systemic conditions, including psoriatic arthritis and increases the risk of cardiovascular disease, metabolic syndrome, cancer, and depression. Psoriasis has been estimated to affect 0.05%-6.6% of people worldwide however, the incidence of psoriasis in New Zealand is unknown. Psoriasis varies widely in severity. Mild psoriasis is usually managed in primary care, however the management of severe psoriasis frequently requires dermatologist input. Topical treatments available for mild chronic plaque psoriasis include topical steroids and calcipotriol, a vitamin D analogue. Treatments for moderate to severe psoriasis used in secondary care include phototherapy and systemic anti-inflammatory medications. biologic medications, such as secukinumab, are a recent development and used for recalcitrant disease, The funding for biologics is only available with a dermatologist’s recommendation. Patient access to hospital and private dermatologists in New Zealand is limited, so many patents who would qualify and benefit from specialist review and treatments do not receive them. We wish to see if non-Caucasian ethnicities, such as Māori, and those living rurally are disadvantaged.

Aims

We plan to conduct a retrospective cross-sectional study to estimate the incidence and severity of chronic plaque psoriasis in New Zealand, including the variation between different regions of the country and the demographics of those affected.

We aim to determine the equity of care of patients with psoriasis in different regions of New Zealand and among different ethnic and socioeconomic groups, especially Māori.

Methods

We will collect the drug dispensing data held by the Ministry of Health for secukinumab, calcipotriol ointment and calcipotriol + betamethasone dipropionate formulations which are medications used explicitly for psoriasis. The national database contains information on all publicly-funded dispensing from any pharmacy of medication that have been prescribed for patients’ personal use. The data will be collected by contacting the Ministry of Health and requesting the information through a data analyst. For each medication, we will assess the patient’s age at dispensing, sex, ethnicity, DHB of domicile and the DHB funding the medication. We will record the medication prescriber (dermatologist, GP, or other), and for how long the medication was continued in each patient. An estimate of equity by ethnicity and location will be established using New Zealand census and New Zealand deprivation index data.

Using established biostatistical techniques, it is possible to establish disease incidence based on dispensing data. These techniques will be used to establish an estimate of the incidence and severity of psoriasis in the New Zealand population. We expect our research to emphasise the need for dermatology services to areas of the country that are undertreated and with high number of patients with psoriasis.

Media Summary

Psoriasis is a common inflammatory condition of the skin and nails that affects people of all ages and ethnicities. It can affect other parts of the body and cause problems like psoriatic arthritis. Psoriasis also increases the risk of cardiovascular disease, metabolic syndrome, cancer, and depression. Psoriasis can prevent people from working, studying, and living their everyday lives. People with moderate to severe disease should be treated by a specialist dermatologist. It is currently not known who or how many people have psoriasis in New Zealand. Based on overseas estimates, psoriasis may affect around 1-3% of the population. In New Zealand, this would be approximately 50,840 – 152,000 people. Overseas studies also suggest that people of non-Caucasian ethnicity tend to receive less treatment and have more severe disease. In New Zealand, access to hospital or private dermatologists is very limited. We wish to examine if there are many people who have undertreated psoriasis, especially those who live in rural areas or are of non-Caucasian ethnicity, such as Māori. Our research aims to estimate the incidence of psoriasis in New Zealand, the number of people with moderate to severe disease, and their demographics. This will identify areas of need and help to plan and allocate healthcare services.

Outcome Statement

Research into the epidemiology of psoriasis and equity of care for this common disorder has not previously been undertaken in New Zealand. We expect our research to strongly emphasise the need for dermatology services to areas of the country that are undertreated and with high number of patients with psoriasis. Our research will also directly influence and inform planning for targeted services for Māori patients. The data will be important for patients as well as planning for both primary care and secondary care. The information will be applicable not only for dermatology, but also reflect on the other medical specialties that are involved in caring for patients with psoriasis, such as general practice, rheumatology, and cardiology.

The epidemiology data is expected to guide future studies and add to the knowledge base of psoriasis worldwide.