Cascade testing effectively identifies undiagnosed sickle cell disease in The Gambia: a quality improvement project.

Abstract

Objective: Sickle cell disease (SCD) has a high mortality during childhood in many low and middle-income countries (LMICs). Early diagnosis improves outcomes but newborn screening is not well established in LMICs. Cascade testing may be feasible and effective in identifying undiagnosed SCD and carriers of haemoglobin (Hb) S.

Design: Quality improvement project using existing clinic and laboratory resources.

Setting: The Haematology Clinic at the Edward Francis Small Teaching Hospital, Banjul, The Gambia.

Participants: Families of index cases with SCD.

Methods: Hb phenotype was determined in full or half-siblings of a SCD index case over a 6-week period using the HemoTypeSC test and confirmed by Hb electrophoresis.

Main outcome measure: Identifying undiagnosed SCD.

Results: Of 102 families invited, 31 (30%) attended during the study period and 53 siblings were tested. Except for one indeterminate test, HemoType SC agreed with Hb electrophoresis. Ten (19%; 95% CI 10 to 32) siblings were diagnosed with HbSS, 25 (47%; 34 to 60) as carriers (HbAS) and 18 (34%; 23 to 48) were unaffected (HbAA). Some symptoms and signs of SCD occurred significantly more frequently in HbSS than in HbAA and HbAS, but none was sufficiently common to help in identifying children for testing.

Conclusions: Cascade testing was effective in identifying undiagnosed HbSS as well as children carrying the sickle cell gene. In routine care settings in LMICs, cascade testing facilitated by point-of-care tests may be feasible and affordable in increasing the detection of SCD and improving outcomes through earlier diagnosis.