Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare disease of peripheral nerves, leading to weakness and numbness. People with CIDP can have difficulty in completing daily activities and may have a lower quality of life. Treatments for CIDP include corticosteroids, plasma exchange (a type of blood transfusion), and intravenous (IV) immunoglobulins (IVIgs). Some people will not respond to these treatments, which is known as having refractory disease. People with refractory disease are offered other treatments, including some that work on the immune system
The care provided to people with CIDP is expensive, costing nearly £50,000 a year per patients in a study conducted in 2007. An updated assessment of costs in patients with CIDP is warranted. Similarly, with development of new treatments for CIDP, it is also important to understand current treatment patterns.
This study aims to understand the current CIDP patient population in England, including their demographic and clinical characteristics, treatment patterns, healthcare resource use, and direct medical costs, particularly in patients who are refractory to first-line therapy. Findings from this study will: (1) help understand treatment patterns, and the clinical and economic burden of CIDP based on current standard of care, and (2) help understand whether there is an unmet need for novel treatments.
Data on treatment patterns, healthcare burden and associated costs is limited and outdated for patients with CIDP. Updated assessments based on the current standard of care are needed to better understand the CIDP patient population in England, including their demographic and clinical characteristics, treatment patterns, HCRU, and direct medical costs, particularly in patients who are refractory to first-line therapy.
Data from the UK Clinical Practice Research Datalink (CPRD) Aurum, HES (Admitted Patient Care [APC], Outpatient [OP], and Accident and Emergency [A&E]), Office for National Statistics (ONS), and the patient-level Index of Multiple Deprivation (IMD) will be used.
Patients aged ≥18 years with a diagnosis of CIDP will be included. Outcomes will include treatment patterns (by line of therapy), discontinuation, switching, and duration of therapy, all-cause and CIDP-specific HCRU and costs. These outcomes will be assessed in all patients with CIDP who received treatment, and in patients refractory to first-line therapies. HCRU and costs will also be assessed among patients who did not receive any treatment for CIDP.
The demographic and clinical characteristics of patients will be summarized descriptively. For each treatment for CIDP, we will describe the number and proportion of patients who experience treatment switch or discontinuation. The Kaplan-Meier (KM) method will be applied to derive the cumulative incidence and empirical distribution of time to each treatment outcome. Both all-cause and CIDP-specific HCRU will be summarized using the number and proportion of patients utilizing each healthcare resource. Event rates per 100 person-years (PYs) will also be calculated. For relevant all-cause and CIDP-specific HCRU, costs will be estimated by multiplying estimates of HCRU by the corresponding unit costs in 2021 obtained from various sources.
The study findings will benefit patients in England by filling a knowledge gap on treatment patterns, HCRU and associated costs based on current standard of care.
Treatment patterns: The following outcomes will be assessed among all patients with CIDP who received treatment, and those who became refractory to first-line therapies:
Treatments received: Treatments of interest in the CPRD data will be identified using product codes. Specific treatments are not available in HES; however, OPCS codes will be used to capture treatments where possible. Lines of therapy will also be described. First-line therapy will be defined as the first prescription of specific treatments for CIDP following the index date (which will be defined as 90 days prior to the date of earliest diagnosis of CIDP). Patients may receive a combination of treatments within a single line of therapy, defined as more than one treatment prescribed/administered within seven days. Additional treatments commenced outside of the seven-day window will be considered a new line of therapy, as will treatment switches (defined below). If one treatment within a combination is stopped, the line of therapy will continue until there is an additional treatment, a switch, or all therapies have been discontinued.
Treatment discontinuation (oral therapies): Discontinuation will be defined as a medication/prescription gap of >90 days after the end of a prescribed days’ supply (‘duration of treatment in days’ variable in CPRD Aurum). The date of discontinuation will be defined as the date of the last prescription plus the number of days’ supply of that last prescription. A prescription date >90 days after the end of a prescribed supply will be considered a new treatment line.
Treatment discontinuation (IV and subcutaneous [SC] therapies): IV and SC therapies will typically only be prescribed or administered as a one-day supply, and the regimens have longer gaps than oral therapies (up to eight weeks). The date of discontinuation will be defined as the date of the last prescription or administration. A new prescription or administration date >90 days after the last prescription/administration will be considered a new treatment line.
Treatment switching: Switching will be defined as a change in treatment to a new drug/medication other than the first/current treatment without a refill of that first/current treatment. The new drug must be prescribed after the last prescription of the index drug treatment and within 90 days after the end of supply of the index drug. Switches to different preparations of the same drug will not be taken into consideration.
Duration of therapy: The duration for each CIDP treatment will be calculated as the time difference (in days) between the corresponding treatment end and start dates. For oral treatments, the duration of therapy will be estimated using the information on package size and the number of packages prescribed. Overlapping prescriptions’ days’ supply will be added together to account for potential stockpiling of drugs i.e., if a patient has a new prescription for the same therapy before a previous prescription’s days’ supply ends, the new prescription will be assumed to initiate at the end of the previous prescription’s days’ supply for the same therapy of interest.
HCRU and direct medical costs: The following outcomes will be assessed among all patients with CIDP who received treatment, among all patients who did not receive treatment, and among those who became refractory to first-line therapies:
Primary care visits: Defined as all-cause and CIDP-specific counts of primary care consultations recorded in CPRD Aurum
Nurse visit: Defined as all-cause and CIDP-specific primary care visits with a nurse recorded in CPRD Aurum
GP visit: Defined as all-cause and CIDP-specific primary care visits with a GP recorded in CPRD Aurum
Telephone consultation: Defined as all-cause and CIDP-specific primary care telephone consultations recorded in CPRD Aurum
Inpatient admissions: Defined as all-cause and CIDP-specific counts of inpatient admissions with at least 1 overnight stay recorded in HES APC
Any inpatient admission: Defined as all-cause and CIDP-specific inpatient admissions recorded in HES APC
ICU admission: Defined as all-cause and CIDP-specific ICU admissions recorded in HES APC
Hospital length of stay: Defined as the number of days from hospital admission to discharge in HES APC for all-cause and CIDP-specific stays
A&E visits: Defined as counts of emergency room visits recorded in HES A&E
Specialist OP visits: Defined as counts of any specialist OP visit recorded in HES OP
Immunology: Defined as immunology specialist visits recorded in HES OP
Neurology: Defined as neurology specialist visits recorded in HES OP
Pain management services: Defined as pain specialist visits recorded in HES OP
Primary care prescriptions: Defined as count of prescription medications used to treat CIDP, plus other most commonly prescribed drugs (up to 30 unique substances in total), as recorded in CPRD
Procedures: Defined as Hematopoietic stem cell transplantation, plasma exchange, and IV infusions, plus other most commonly performed procedures (up to 20 in total), as recorded in HES using OCPS codes
Direct medical costs: Defined as all-cause and CIDP-specific (where possible) cost in £GBP for each of the HCRU variables specified above. The Following sources will be used to complement data available in CPRD and HES:
• Drug prices (up to 30 most commonly used drugs): British National Formulary; NHS Drug Tariff; eMIT Database; and MIMS Database
• Consultation visits: Unit Costs of Health and Social Care by L. Curtis; PSSRU; NHS Reference Costs, UK Department of Health; and NHS National Tariff Payment System
• Hospital days: NHS Reference Costs, UK Department of Health; and NHS National Tariff Payment System
• Diagnostic and therapeutic procedures (up to 20 most common procedures): NHS Reference Costs, UK Department of Health; and NHS National Tariff Payment System
F. Omar Saeed - Chief Investigator - Sanofi Winthrop Industrie (France)
Harmony Omeife - Corresponding Applicant - Evidera, Inc
Dimitra Lambrelli - Collaborator - Evidera, Inc
Mark Yates - Collaborator - Evidera Ltd - UK
Natalia Petruski-Ivleva - Collaborator - Sanofi Winthrop Industrie (France)
Robert Donaldson - Collaborator - Evidera Ltd - UK
Sophie Guillonneau - Collaborator - Sanofi Winthrop Industrie (France)
HES Accident and Emergency;HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation