Hemoglobin Desaturation in Sickle Cell Disease

Study Overview
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Brief Summary
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As part of routine care for SCD, some people are found to have low oxygen levels (≤ 88%) while sleeping, at rest, or with exercise. Testing is done with a small portable device positioned on the finger that measures oxygen levels during sleep, at rest, or following exercise. The investigators start oxygen treatment for people with low levels of oxygen. As a part of this study, the investigators will find out if any changes in cell stickiness occur with low oxygen levels (at rest, at night, or with exertion) and if cells become less sticky with oxygen treatment. Study subjects will be seen before testing and 2 months after testing. In some cases (people with low oxygen levels during testing), study subjects will have been prescribed oxygen, and the investigators will test the effects of that treatment on the stickiness of red cells.

Detailed Description
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In SCD, exertional hypoxia and nocturnal hemoglobin desaturation (NHD, or hemoglobin deoxygenation during sleep) are common, treatable, and associated with bad outcomes in children and young adults15,16. The median life-expectancy of SCD has risen dramatically in the last 40 years. One consequence of this is an expanding young adult population in whom the comorbidities are not yet fully characterized. The prevalence, clinical consequences, and treatment outcomes of exertional hypoxia and NHD are poorly described in adults with SCD. Therefore, it is important to identify and better understand any clinically significant hypoxia (during exercise or sleep or at rest) in this expanding adult population. The investigators will study whether RBC adhesion at baseline and when exposed to hypoxia in vitro is significantly increased in adult HbSS patients with baseline hypoxia, exertional hypoxia or nocturnal NHD due to RBC membrane changes arising from prolonged in vivo exposure to hypoxia, which may be mitigated by oxygen therapy. Hypotheses: The investigators hypothesize that disease activity and RBC adhesion (under normoxia) will be greater in subjects with HbSS plus baseline in vivo hypoxia, exertional hypoxia, or NHD, due to RBC membrane damage from prolonged hypoxia in vivo. Successful treatment with therapeutic oxygen, at baseline, with exertion, or during sleep, may decrease RBC adhesion in vitro. Specific Aim 1: To evaluate for resting hypoxia, exertional hypoxia or NHD, and its clinical associations, in adults with HbSS. Specific Aim 2: To examine baseline RBC adhesion under normoxia or hypoxia in vitro in adults with HbSS, with and without in vivo resting or exertional hypoxia or NHD. Specific Aim 3: To examine serial changes in S-RBC adhesion at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. The investigators are testing whether: Subjects with Hb desaturation at baseline, with exertion, or during sleep (NHD), compared to those without, will have increased disease activity (exertional or nocturnal symptoms, priapism, WBC activation, reticulocytosis, and/or hemolysis). S-RBCs from subjects with clinical Hb desaturation at rest, with exertion, or during sleep, compared to those without, will have increased adhesion at baseline and when exposed to hypoxia in vitro. 2.A. Treatment of baseline hypoxia, exertional hypoxia, and/or NHD with supplemental oxygen will decrease S-RBC adhesion and HEA, and may decrease symptoms, especially night- time symptoms.

Official Title
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Hemoglobin Desaturation and RBC Adhesion: Potential Therapeutic Targets in Sickle Cell Disease

Conditions
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Sickle Cell Disease

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Male or Female > 18 year of age at the time of consent. Documentation of Sickle Cell Disease, phenotypically HbSS (including S-Beta 0 thalassemia) Written informed consent (and assent when applicable) obtained from subject or subject's legal representative and ability for subject to comply with the requirements of the study. English speaking patient Exclusion Criteria: Ongoing Oxygen therapy. active pregnancy, due to complex pathophysiology during that interval. Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data. -

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Evaluation for resting hypoxia | We will test resting SpO2 and night-time oxymetry to obtain Hb saturation results. | Through study completion, up to approximately 4 years | 
| Evaluation for exertional hypoxia | We will evaluate 6MWT results and obtain Hb saturation results. | Through study completion, up to approximately 4 years | 
| Evaluation of hypoxia and its effect on CBC | CBC results will be evaluated | Through study completion, up to approximately 4 years | 
| Evaluation of hypoxia and its effect on reticulocyte count | Reticulocyte count will be evaluated | Through study completion, up to approximately 4 years | 
| Evaluation of hypoxia and its effect on LDH | LDH level will be evaluated | Through study completion, up to approximately 4 years | 
| Evaluation of hypoxia and its effect on serum chemistry | Serum chemistry through a comprehensive panel will be evaluated | Through study completion, up to approximately 4 years | 
| Evaluation of patient's incidence of hypoxia-related symptoms | Incidence of hypoxia-related symptoms will be obtained from review of the patient's chart and approved symptom questionnaire. | Through study completion, up to approximately 4 years | 
| Evaluation of hypoxia and its effect on echocardiogram results | Screening echocardiogram | Through study completion, up to approximately 4 years | 
| Evaluation of patient's incidence of hypoxia-related nocturnal symptoms | Incidence of nocturnal hypoxia-related symptoms will be obtained from review of the patient's chart and approved symptom questionnaire. | Through study completion, up to approximately 4 years | 
| Examination of amount of baseline RBC adhesion and HEA in vitro in adults with HbSS | Amount of S-RBC adhesion to LN on the SCD and Hypoxia Biochips will be quantitated, using <400 μL surplus whole blood in EDTA, obtained during routine clinical care (as published previously1,6-8), at the clinic visit immediately prior to night-time oximetry and 6MWT | Through study completion, up to approximately 4 years | 
| Examination of baseline FACS results in adults with HbSS | Fluorescent Activated Cell Sorting (FACS) following incubation with antibodies to CD14, CD16, and CX3CR1 will be performed on 3-400 μL of surplus whole blood. | Through study completion, up to approximately 4 years | 
| Examination of amount of baseline RBC adhesion and HEA in vitro in adults with HbSS | Simple t-tests will be used to compare RBC adhesion, HEA to LN and monocyte activation in patients with clinically significant hypoxia and those without any hypoxia | Through study completion, up to approximately 4 years | 
| Examination of serial changes in incidence of nocturnal symptoms at baseline and with hypoxia, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | At  2 months after initial testing (and >6 weeks on treatment, if needed), all subjects will be re-evaluated for incidence of hypoxia-related nocturnal symptoms through review of the patient's chart and approved symptom questionnaire | 2 months | 
| Examination of serial changes in amount of S-RBC adhesion at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen | At  2 months after initial testing (and >6 weeks on treatment, if needed), all subjects will be re-evaluated for amount of RBC adhesion | 2 months | 
| Examination of serial changes in incidence of hypoxia-related symptoms at baseline and with hypoxia, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | At  2 months after initial testing (and >6 weeks on treatment, if needed), all subjects will have incidence of hypoxia-related symptoms re-evaluated through review of the patient's chart and approved symptom questionnaire | 2 months | 
| Examination of serial changes in Hb saturation at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen | We will repeat Hb saturation testing | 2 months | 
| Examination of serial changes in amount of S-RBC adhesion at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | Paired t-test on S-RBC adhesion to LN and HEA before and after oxygen therapy, in subjects with and without clinically significant hypoxia will be performed | 2 months | 
| Examination of serial changes in amount of WBC activation at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen | Amount of WBC activation will be determined | 2 months | 
| Examination of serial changes in CBC at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | CBC results will be examined for any suggestive changes | 2 months | 
| Examination of serial changes in reticulocyte count at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | Reticulocyte count will be examined for any suggestive changes | 2 months | 
| Examination of serial changes in LDH at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | LDH level will be examined for any suggestive changes | 2 months | 
| Examination of serial changes in serum chemistry at baseline and with hypoxia in vitro, in adults with HbSS and resting or exertional hypoxia or NHD, before and after therapeutic intervention with oxygen. | Serum chemistry through a comprehensive panel will be examined for any suggestive changes | 2 months |