An observational study in Sickle Cell Disease, sponsored by Pfizer. Completed at 4 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-06-10.
Sponsored by Pfizer · Observational
The purpose of this clinical trial is to evaluate the performance of the sickle cell disease (SCD) electronic diary in people with SCD who are on treatment that will change SCD and those not on such a treatment.
SCD is a type of condition when there are fewer red blood cells to carry oxygen around the body.
This disease can be passed on from parent to child and may cause pain, infections and damage to organs.
This study is seeking participants who:
1,134 studies on the registry are indexed under Anemia, Sickle Cell; 238 are open to participants now.
This study's enrollment of 98 is close to the median of 100 across 296 observational studies indexed under Anemia, Sickle Cell.
Browse Anemia, Sickle Cell studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Participants with a confirmed diagnosis of stable Sickle Cell Disease (SCD) (hemoglobin S inherited from both parents [HbS/S] or hemoglobin S inherited from one parent and hemoglobin beta thalassemia inherited from the other parent [HbS/beta-zero-thalassemia] genotype) who are either not on disease modifying treatment or on a stable dose of a SCD disease modifying treatment regimen.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
- Confirmed diagnosis of stable SCD (HbS/S or HbS/beta-zero-thalassemia).
Additional Inclusion Criteria (No Disease Modifying Treatment Control Group):
Additional Inclusion Criteria (SCD Disease Modifying Treatment Group):
Must be on a stable dose of their SCD treatment regimen ≥8 weeks prior to Day 1 with the intent of remaining on the same dose throughout the study, unless adjustments are medically necessary due to bone marrow suppression, in accordance with published guidelines and/or product specific guidance (eg, package label). Accepted SCD disease modifying treatment regimens include:
Exclusion Criteria (All Groups):
Additional Exclusion Criteria (No Disease Modifying Treatment Control Group):
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
The number of neutrophils, white blood cells that help fight infection, in a given amount of blood. Too few raises the risk of infection.
It is a count, not a percentage of the white cells. Limits are written in units that mean the same: ≥ 1.5 × 10⁹/L is ≥ 1,500 per mm³ (µL). Each lab has its own reference range.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Absolute neutrophil count (ANC)
The number of neutrophils, white blood cells that help fight infection, in a given amount of blood. Too few raises the risk of infection.
It is a count, not a percentage of the white cells. Limits are written in units that mean the same: ≥ 1.5 × 10⁹/L is ≥ 1,500 per mm³ (µL). Each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
SCD participants not on disease modifying treatment.
Other: Electronic Diary
SCD participants on a stable dose of a SCD disease modifying treatment regimen.
Other: Electronic Diary
Participants will be asked to complete a daily electronic patient reported outcome diary entry to report on their experience in the past 24 hours.
Also known as: SCD electronic patient reported outcome (ePRO)
Physician-reported Medical Utilization (MU) Vaso-occlusive Crisis (VOC) Rate
Physician-reported MU VOC: defined as an acute episode of pain with no other cause other than a VOC event that required a medical facility visit or contact with a health care professional and treatment with oral or parenteral narcotics, or non-steroidal anti-inflammatory drugs. Acute chest syndrome, hepatic sequestration, splenic sequestration, and priapism (requiring a visit to a medical facility) were also considered MU VOC. Contact with healthcare professional included: called healthcare provider (or telemedicine visit) and received treatment, went to clinic and received treatment, went to emergency department and received treatment, admitted to the hospital and received treatment. VOC rate was derived as annualized rate. Annualized MU VOC rate = (Number of MU VOC events \* 365)/ (number of days in the observation period).
Time frame: Baseline up to Day 180
VOC Day Rate
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was a self-report by the participant of experiencing a VOC during the past 24 hours. This was assessed through a dichotomous (Yes/No) item on the SCD ePRO system, "Did you have a pain crisis in the past 24 hours?" A response of "Yes" indicated a VOC day. VOC day rate was derived as annualized rate. VOC day rate = (Number of VOC days \* 365)/ (number of days in the observation period).
Time frame: Baseline up to Day 180
Patient-reported VOC Event Rate
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. Patient reported VOC Event is used to define a sequence of VOC days that could also include single intervening days with no pain crisis. The subsequent occurrence of two consecutive days with no pain crisis operationally defines the end of the respective VOC event. Rate were derived as annualized rate. Annualized VOC event rate = (Number of VOC events \* 365)/ (number of days in the observation period).
Time frame: Baseline up to Day 180
Sickle Cell Disease (SCD) Electronic Patient Reported Outcome (ePRO) Daily Worst Pain Scores by VOC Status
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. Participants rated their pain by selecting the one number that best described their pain at its worst in the past 24 hours from 0-10, where 0= no pain and 10= as bad as you can imagine. Higher scores indicated worse pain. Data in this outcome measure was presented separately for VOC state and non-VOC state.
Time frame: Baseline up to Day 180
Sickle Cell Disease Electronic Patient Reported Outcome Daily Worst Tiredness Scores by VOC Status
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. Participants rated their tiredness by selecting the one number that best described their tiredness at its worst in the past 24 hours from 0-10, where 0= no tiredness and 10= as bad as you can imagine. Higher scores indicated worse tiredness. Data in this outcome measure was presented separately for VOC state and non-VOC state.
Time frame: Baseline up to Day 180
Sickle Cell Disease Electronic Patient Reported Outcome Daily Rating for Ability to Perform Usual Physical Activity (UPA) by VOC Status
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. A measure of participant's ability to perform their UPA (e.g. walking, climbing stairs, or household chores) during a VOC event was assessed on SCD ePRO recorded by participants using a scale ranging from 1-4 scale, where 1= able to perform with no difficulty and 4= unable to perform usual physical activities, where higher score indicated worse status. Data in this outcome measure was presented separately for VOC state and non-VOC state.
Time frame: Baseline up to Day 180
Percent Change in Physician-reported MU VOC Rate Per Unit of Change in VOC Day Rate
MU VOC: acute episode of pain with no other cause other than VOC event that required medical facility visit/contact with health care professional and treatment with oral/parenteral narcotics/NSAIDs. Acute chest syndrome,hepatic/splenic sequestration, priapism also considered MU VOC. MU VOC derived as annualized rate by:(Number of MU VOC events\*365)/(number of days in observation period). VOC day rate: VOC day was self-report by participant experiencing VOC during past 24 hours. It was assessed by dichotomous (Yes/No) item on SCD ePRO system, "Did you have pain crisis in past 24 hours?" Response "Yes" indicated VOC day. VOC day rate derived as annualized rate by: (Number of VOC days\*365)/(number of days in observation period). Parameter of interest was % change of MU VOC rate per unit of change in VOC Day rate. It was estimated via Negative Binomial model to evaluate association between physician-reported MU VOC rate and SCD ePRO VOC Day rate and was reported with corresponding 95% CI.
Time frame: Baseline up to Day 180
Percent Change in Physician-reported MU VOC Rate Per Unit of Change in Patient-reported VOC Event Rate
MU VOC: acute episode of pain with no other cause other than VOC event that required medical facility visit/contact with health care professional and treatment with oral/parenteral narcotics/NSAIDs. Acute chest syndrome, hepatic/splenic sequestration, priapism also considered MU VOC. MU VOC derived as annualized rate by:(Number of MU VOC events\*365)/(number of days in observation period). VOC Event rate: Patient-reported VOC Event is used to define a sequence of VOC days. The subsequent occurrence of two consecutive days with no pain crisis operationally defines the end of the respective VOC event. Rate were derived as annualized rate by: (Number of VOC events \* 365)/ (number of days in the observation period). Parameter of interest was % change of MU VOC rate per unit of change in VOC Event rate. It was estimated via Negative Binomial model to evaluate association between physician-reported MU VOC rate and SCD ePRO VOC Event rate and was reported with corresponding 95% CI.
Time frame: Baseline up to Day 180
Participants with stable sickle cell disease (SCD) (hemoglobin S inherited from both parents \[HbS/S\] or hemoglobin S inherited from one parent and hemoglobin beta thalassemia inherited from the other parent \[HbS/beta-zero-thalassemia\] genotype) were enrolled in two concurrent groups and were observed for 6 months in this study. This was an observational study, and under this study no therapeutic study interventions were administered.
| Milestone | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Started | 33 | 65 |
| Evaluable analysis population | 32 | 65 |
| Completed | 32 | 64 |
| Not completed | 1 | 1 |
| Withdrew: Adverse event | 1 | 0 |
| Withdrew: Protocol violation | 0 | 1 |
Physician-reported MU VOC: defined as an acute episode of pain with no other cause other than a VOC event that required a medical facility visit or contact with a health care professional and treatment with oral or parenteral narcotics, or non-steroidal anti-inflammatory drugs. Acute chest syndrome, hepatic sequestration, splenic sequestration, and priapism (requiring a visit to a medical facility) were also considered MU VOC. Contact with healthcare professional included: called healthcare provider (or telemedicine visit) and received treatment, went to clinic and received treatment, went to emergency department and received treatment, admitted to the hospital and received treatment. VOC rate was derived as annualized rate. Annualized MU VOC rate = (Number of MU VOC events \* 365)/ (number of days in the observation period).
| Events per year | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Physician-reported Medical Utilization (MU) Vaso-occlusive Crisis (VOC) Rate | 2.02 (0.00 to 58.60) | 2.02 (0.00 to 60.55) |
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was a self-report by the participant of experiencing a VOC during the past 24 hours. This was assessed through a dichotomous (Yes/No) item on the SCD ePRO system, "Did you have a pain crisis in the past 24 hours?" A response of "Yes" indicated a VOC day. VOC day rate was derived as annualized rate. VOC day rate = (Number of VOC days \* 365)/ (number of days in the observation period).
| Days per year | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| VOC Day Rate | 112.79 (70.06 to 181.59) | 85.06 (52.63 to 137.46) |
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. Patient reported VOC Event is used to define a sequence of VOC days that could also include single intervening days with no pain crisis. The subsequent occurrence of two consecutive days with no pain crisis operationally defines the end of the respective VOC event. Rate were derived as annualized rate. Annualized VOC event rate = (Number of VOC events \* 365)/ (number of days in the observation period).
| Events per year | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Patient-reported VOC Event Rate | 16.22 (11.38 to 23.12) | 22.63 (15.80 to 32.43) |
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. Participants rated their pain by selecting the one number that best described their pain at its worst in the past 24 hours from 0-10, where 0= no pain and 10= as bad as you can imagine. Higher scores indicated worse pain. Data in this outcome measure was presented separately for VOC state and non-VOC state.
| Score on a scale | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| VOC State | 6.0 (5.1 to 6.9) | 6.4 (5.6 to 7.3) |
| Non-VOC State | 2.4 (1.6 to 3.3) | 2.9 (2.0 to 3.8) |
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. Participants rated their tiredness by selecting the one number that best described their tiredness at its worst in the past 24 hours from 0-10, where 0= no tiredness and 10= as bad as you can imagine. Higher scores indicated worse tiredness. Data in this outcome measure was presented separately for VOC state and non-VOC state.
| Score on a scale | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| VOC State | 5.0 (4.1 to 6.0) | 5.6 (4.7 to 6.5) |
| Non-VOC State | 3.4 (2.5 to 4.3) | 3.5 (2.6 to 4.4) |
A VOC was a complication of SCD characterized by vaso-occlusion presenting as recurrent pain episodes. VOC day was defined as the day on which a SCD participant self-reports sickle pain crisis that was recorded in the SCD ePRO. A non-VOC day was defined as the day on which a SCD participant does not self-reports sickle pain crisis. A measure of participant's ability to perform their UPA (e.g. walking, climbing stairs, or household chores) during a VOC event was assessed on SCD ePRO recorded by participants using a scale ranging from 1-4 scale, where 1= able to perform with no difficulty and 4= unable to perform usual physical activities, where higher score indicated worse status. Data in this outcome measure was presented separately for VOC state and non-VOC state.
| Score on a scale | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| VOC State | 2.3 (2.1 to 2.4) | 2.4 (2.3 to 2.6) |
| Non-VOC State | 1.3 (1.1 to 1.4) | 1.4 (1.2 to 1.5) |
MU VOC: acute episode of pain with no other cause other than VOC event that required medical facility visit/contact with health care professional and treatment with oral/parenteral narcotics/NSAIDs. Acute chest syndrome,hepatic/splenic sequestration, priapism also considered MU VOC. MU VOC derived as annualized rate by:(Number of MU VOC events\*365)/(number of days in observation period). VOC day rate: VOC day was self-report by participant experiencing VOC during past 24 hours. It was assessed by dichotomous (Yes/No) item on SCD ePRO system, "Did you have pain crisis in past 24 hours?" Response "Yes" indicated VOC day. VOC day rate derived as annualized rate by: (Number of VOC days\*365)/(number of days in observation period). Parameter of interest was % change of MU VOC rate per unit of change in VOC Day rate. It was estimated via Negative Binomial model to evaluate association between physician-reported MU VOC rate and SCD ePRO VOC Day rate and was reported with corresponding 95% CI.
| Percent change | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Percent Change in Physician-reported MU VOC Rate Per Unit of Change in VOC Day Rate | 2.4987 | 2.5941 |
MU VOC: acute episode of pain with no other cause other than VOC event that required medical facility visit/contact with health care professional and treatment with oral/parenteral narcotics/NSAIDs. Acute chest syndrome, hepatic/splenic sequestration, priapism also considered MU VOC. MU VOC derived as annualized rate by:(Number of MU VOC events\*365)/(number of days in observation period). VOC Event rate: Patient-reported VOC Event is used to define a sequence of VOC days. The subsequent occurrence of two consecutive days with no pain crisis operationally defines the end of the respective VOC event. Rate were derived as annualized rate by: (Number of VOC events \* 365)/ (number of days in the observation period). Parameter of interest was % change of MU VOC rate per unit of change in VOC Event rate. It was estimated via Negative Binomial model to evaluate association between physician-reported MU VOC rate and SCD ePRO VOC Event rate and was reported with corresponding 95% CI.
| Percent change | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Percent Change in Physician-reported MU VOC Rate Per Unit of Change in Patient-reported VOC Event Rate | 1.4529 | 7.3506 |
Collected over Day 1 up to Day 180. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Control Group | 0/32 (0%) | 0/32 (0%) | 0/32 (0%) |
| Disease-Modifying Treatment Group | 0/65 (0%) | 0/65 (0%) | 1/65 (1.5%) |
| Event | Control Group | Disease-Modifying Treatment Group |
|---|---|---|
| Procedural painInjury, poisoning and procedural complications | 0/32 | 1/65 |
Evaluable Analysis population included all participants who signed the informed consent document and met the eligibility criteria.
| Age, Categorical(Participants) | Control Group | Disease-Modifying Treatment Group | Total |
|---|---|---|---|
| <=18 years | 0 | 0 | 0 |
| Between 18 and 65 years | 32 | 63 | 95 |
| >=65 years | 0 | 2 | 2 |
| Sex: Female, Male(Participants) | Control Group | Disease-Modifying Treatment Group | Total |
|---|---|---|---|
| Female | 26 | 39 | 65 |
| Male | 6 | 26 | 32 |
| Ethnicity (NIH/OMB)(Participants) | Control Group | Disease-Modifying Treatment Group | Total |
|---|---|---|---|
| Hispanic or Latino | 1 | 3 | 4 |
| Not Hispanic or Latino | 23 | 43 | 66 |
| Unknown or Not Reported | 8 | 19 | 27 |
| Race (NIH/OMB)(Participants) | Control Group | Disease-Modifying Treatment Group | Total |
|---|---|---|---|
| American Indian or Alaska Native | 0 | 0 | 0 |
| Asian | 0 | 0 | 0 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 |
| Black or African American | 31 | 62 | 93 |
| White | 0 | 1 | 1 |
| More than one race | 0 | 0 | 0 |
| Unknown or Not Reported | 1 | 2 | 3 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
This study is completed, as verified in May 2026. You cannot join it, but the record below documents what was studied.
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