The Neuropeptide Substance P is Elevated in Sickle Cell Disease and is a Marker of Severity of Vaso-occlusive Crisis.

Background: Acute episode of pain is the most frequent symptom for which patients with sickle cell disease (SCD) seek medical attention. The neuropeptide Substance P (SP) has been suggested as a possible aetiologic factor. This study compared the serum levels of SP in SCD subjects in painful vaso-occlusive crisis with those in steady state and normal HbAA subjects.

Methodology: This case-controlled study investigated eighteen SCD patients in vaso-occlusive crisis (VOC) and eighteen in steady state, while fourteen HbAA subjects were recruited as controls. Blood was collected in plain bottles and subsequently, the serum was separated for SP assay using the ELISA technique. Each sample was run, and results were confirmed in duplicate. Optical density was read at an absorbance of 450nm.

Results: The study showed that SP was significantly higher in SCD patients in steady state (184.79±18.67ng/L versus 104.17±19.24ng/L) compared to the controls (t=2.97, p=0.006); while the values obtained in those in VOC (375.78±76.21ng/L) were also significantly higher (t=2.433, p=0.02) than those in steady state (184.79±18.67ng/L). The SP value in the SCD patients in VOC was almost twice as much as those in steady state and about three times as much as the value in the controls and the differences were statistically significant (t=7.72, p=0.001).

Conclusion: The study showed significantly higher SP levels in VOC compared to steady state or HbAA subjects suggesting that SP may be a marker for pain sensitisation.