The present study is a non-interventional retrospective chart review study assessing the prevalence of PNH-clones in patients with PNH risk-factors aged ≥14 years and treated at our hospital. The objective of this study is to develop a PNH screening tool on the hospital Electronic Health Record (EHR) system. An algorithm defining PNH risk groups is developed.

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a life-threatening hematological disorder, but with an effective therapy. Prevalence is estimated between 1-5 per million people, often manifested by cardiovascular, gastrointestinal, neurological or haematological symptoms. Referral is therefore typically to several specialists, resulting in PNH underdiagnosis.

This chart review study consists primarily of developing an algorithm to identify a high-risk cohort of potential PNH patients who need treatment from all registered patients, with maximum ability to find relevant cases. Secondly, this cohort will be manually reviewed by clinicians for final screening. The challenge hence is maximizing the ability to find all relevant PNH patients yet limiting the number to ensure manual review is possible.

Inclusion Criteria:

• Patient ≥14 years of age
• At least 1 record encoded in the General Hospital Delta (AZ Delta) patient database (HiX) between 20 April 2018 and 1 March 2022
• A history or presence of at least one PNH risk factors identified following retrospective screening of electronic patient records

Exclusion Criteria:

• None

Eligible patients will be identified by retrospective screening of the hospital's electronic patients records using data search queries based on ICD-10 codes, lab results, keyword search in questionnaires, medical reports, notes, radiology reports & medical diagnoses corresponding to one of the PNH Risk factors described:

1. Patients with evidence of haemolysis without obvious cause
2. Patients with evidence of bone marrow dysfunction
3. Patients with thrombosis