The Prevalence of Isolated Neutropenia at High Altitude in Southern Saudi Arabia: Does Altitude Affect Leucocyte Count?

Introduction: Isolated neutropenia is a common problem in hematology practice. Benign ethnic neutropenia (BEN) is the common form of neutropenia worldwide and it affects mainly African and Middle Eastern ethnicities. Most cases of isolated mild and moderate neutropenia are benign and associated with no clinical significance. The aim of this study was to estimate the prevalence of isolated neutropenia at high-altitude southern Saudi Arabia.

Methods: A large dataset of complete blood counts (CBCs) was analyzed for walk-in patients of both genders, of age ranges from 12 to 60 years doing blood tests at a commercial lab for high altitude - 2,270 meters above sea level - (HA) group, and from sea level SL group. Abnormal biochemical or CBC results were excluded before analysis.

Results: For HA group, 3123 CBCs were analyzed and for SL group 18,427 CBCs were analyzed. The prevalence of mild neutropenia, defined as absolute neutrophil count (ANC) in the range of 1.0-.5× 10⁹/L, was 12.4% (n=399) versus 5.6% (n=1025), while moderate neutropenia, defined as ANC of 0.5-1 × 10⁹/L, was present 6% (n=191) versus 1.45% (n=269) in the high altitude and sea level groups, respectively. Severe neutropenia, defined as neutrophil count less than 0.5-1 × 10⁹/L, was rare in both groups.

Conclusion: Isolated neutropenia is common in Saudis living at high altitude. While benign ethnic neutropenia (BEN) is thought to be the major contributing factor to this high prevalence, other factors including environmental factors and altitude are possible contributing factors along with underlying ethnic neutropenia.