| Summary: | <strong>Background<br></strong>
Regularly transfused people with sickle cell disease (SCD) and people with thalassaemia are at risk of iron overload. Iron overload can lead to iron toxicity in vulnerable organs such as the heart, liver and endocrine glands, which can be prevented and treated with iron‐chelating agents. The intensive demands and uncomfortable side effects of therapy can have a negative impact on daily activities and wellbeing, which may affect adherence.
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Objectives<br></strong>
To identify and assess the effectiveness of different types of interventions (psychological and psychosocial, educational, medication interventions, or multi‐component interventions) and interventions specific to different age groups, to improve adherence to iron chelation therapy compared to another listed intervention, or standard care in people with SCD or thalassaemia.
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Search methods<br></strong>
We searched CENTRAL (Cochrane Library), MEDLINE, PubMed, Embase, CINAHL, PsycINFO, ProQuest Dissertations & Global Theses, Web of Science & Social Sciences Conference Proceedings Indexes and ongoing trial databases (13 December 2021). We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register (1 August 2022).
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Selection criteria<br></strong>
For trials comparing medications or medication changes, only randomised controlled trials (RCTs) were eligible for inclusion.
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For studies including psychological and psychosocial interventions, educational interventions, or multi‐component interventions, non‐randomised studies of interventions (NRSIs), controlled before‐after studies, and interrupted time series studies with adherence as a primary outcome were also eligible for inclusion.
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Data collection and analysis<br></strong>
For this update, two authors independently assessed trial eligibility and risk of bias, and extracted data. We assessed the certainty of the evidence using GRADE.
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Main results<br></strong>
We included 19 RCTs and one NRSI published between 1997 and 2021. One trial assessed medication management, one assessed an education intervention (NRSI) and 18 RCTs were of medication interventions. Medications assessed were subcutaneous deferoxamine, and two oral chelating agents, deferiprone and deferasirox.
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We rated the certainty of evidence as very low to low across all outcomes identified in this review.
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Four trials measured quality of life (QoL) with validated instruments, but provided no analysable data and reported no difference in QoL.
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We identified nine comparisons of interest.
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1. Deferiprone versus deferoxamine<br></strong>
We are uncertain whether or not deferiprone affects adherence to iron chelation therapy (four RCTs, unpooled, very low‐certainty evidence), all‐cause mortality (risk ratio (RR) 0.47, 95% confidence interval (CI) 0.18 to 1.21; 3 RCTs, 376 participants; very low‐certainty evidence), or serious adverse events (SAEs) (RR 1.43, 95% CI 0.83 to 2.46; 1 RCT, 228 participants; very low‐certainty evidence).
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Adherence was reported as "good", "high" or "excellent" by all seven trials, though the data could not be analysed formally: adherence ranged from 69% to 95% (deferiprone, mean 86.6%), and 71% to 93% (deferoxamine, mean 78.8%), based on five trials (474 participants) only.
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2. Deferasirox versus deferoxamine<br></strong>
We are uncertain whether or not deferasirox affects adherence to iron chelation therapy (three RCTs, unpooled, very low‐certainty evidence), although medication adherence was high in all trials.
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We are uncertain whether or not there is any difference between the drug therapies in serious adverse events (SAEs) (SCD or thalassaemia) or all‐cause mortality (thalassaemia).
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3. Deferiprone versus deferasirox<br></strong>
We are uncertain if there is a difference between oral deferiprone and deferasirox based on a single trial in children (average age 9 to 10 years) with any hereditary haemoglobinopathy in adherence, SAEs and all‐cause mortality.
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4. Deferasirox film‐coated tablet (FCT) versus deferasirox dispersible tablet (DT)<br></strong>
One RCT compared deferasirox in different tablet forms. There may be a preference for FCTs, shown through a trend for greater adherence (RR 1.10, 95% CI 0.99 to 1.22; 1 RCT, 88 participants), although medication adherence was high in both groups (FCT 92.9%; DT 85.3%). We are uncertain if there is a benefit in chelation‐related AEs with FCTs.
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We are uncertain if there is a difference in the incidence of SAEs, all‐cause mortality or sustained adherence.
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5. Deferiprone and deferoxamine combined versus deferiprone alone<br></strong>
We are uncertain if there is a difference in adherence, though reporting was usually narrative as triallists report it was "excellent" in both groups (three RCTs, unpooled).
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We are uncertain if there is a difference in the incidence of SAEs and all‐cause mortality.
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6. Deferiprone and deferoxamine combined versus deferoxamine alone<br></strong>
We are uncertain if there is a difference in adherence (four RCTs), SAEs (none reported in the trial period) and all‐cause mortality (no deaths reported in the trial period). There was high adherence in all trials.
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7. Deferiprone and deferoxamine combined versus deferiprone and deferasirox combined<br></strong>
There may be a difference in favour of deferiprone and deferasirox (combined) in rates of adherence (RR 0.84, 95% CI 0.72 to 0.99) (one RCT), although it was high (> 80%) in both groups.
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We are uncertain if there is a difference in SAEs, and no deaths were reported in the trial, so we cannot draw conclusions based on these data (one RCT).
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8. Medication management versus standard care<br></strong>
We are uncertain if there is a difference in QoL (one RCT), and we could not assess adherence due to a lack of reporting in the control group.
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9. Education versus standard care<br></strong>
One quasi‐experimental (NRSI) study could not be analysed due to the severe baseline confounding.
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Authors' conclusions<br></strong>
The medication comparisons included in this review had higher than average adherence rates not accounted for by differences in medication administration or side effects, though often follow‐up was not good (high dropout over longer trials), with adherence based on a per protocol analysis.
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Participants may have been selected based on higher adherence to trial medications at baseline. Also, within the clinical trial context, there is increased attention and involvement of clinicians, thus high adherence rates may be an artefact of trial participation.
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Real‐world, pragmatic trials in community and clinic settings are needed that examine both confirmed or unconfirmed adherence strategies that may increase adherence to iron chelation therapy.
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Due to lack of evidence this review cannot comment on intervention strategies for different age groups.
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