Table 2.

Studies that examined PD medication prescribing determinants only.

Study	Country	Type of study and source of data	PD case ascertainment	Year	Number of patients	Prescribing determinants	Comments/main findings	Quality score (out of 10)
Goudreau et al. [49]	USA	Using data from a clinical trial of creatine vs placebo in participants with early, mild PD on stable doses of dopaminergic therapy (NINDS Exploratory Trials in PD (NET-PD) Long-Term Study-1 (LS1))	PD diagnosis confirmed by clinical experts.	2007–2010 No comparison	1616 patients	Age, gender, race, education level, insurance statue, duration of the disease, comorbidity score, and using of MAO-b inhibitors	This study examined the characteristics of PD patients who enrolled in NET-PD-LS1 study. It compared between patients with L-dopa vs patients with DAs vs patients with a combination therapy (L-dopa + DAs) in terms of proposed prescribing determinates. Higher education level, longer duration of the disease, younger age, and using of MAO-b inhibitors were strongly more common in patients who used DAs.	9
Umeh et al. [52]	USA	Using data from a clinical trial of creatine vs placebo in participants with early, mild PD on stable doses of dopaminergic therapy (NINDS Exploratory Trials in PD (NET-PD) Long-Term Study-1 (LS1))	PD diagnosis confirmed by clinical experts.	2007–2010 No comparison	1741 patients	Gender and education level	This study examined the characteristics of PD patients who enrolled in NET-PD-LS1 study. It compared between patients with L-dopa vs patients with DAs vs patients with a combination therapy (L-dopa + DAs) in terms of proposed prescribing determinates. There was no association between patients' genders and the type of PD medications that were received. There was no association between patients' education levels and the type of PD medications that were received.	6
Chen et al. [76]	China	The cross-sectional questionnaire-based survey was distributed to 612 doctors.	N/A	2010–2011	N/A	Age, type of prescribers, cognitive impairment (CI), and wearing-off phenomenon.	42.9%, 33.5% of doctors preferred using DAs, L-dopa, respectively, for patients aged less than 65 years without CI. 48.3% of doctors preferred switching from immediate release L-dopa to controlled release L-dopa for patient with wearing-off phenomenon. Movement disorder specialists were better than GPs and general neurologists in improving patient quality of care and sticking to national guidelines.	5
Hu et al. [77]	UK	The cross-sectional questionnaire was distributed to 340 PD patients.	PD diagnosis confirmed by clinical experts.	2007–2008	340 patients	Age, cognition, mobility, education level and tremor.	The suboptimal care was defined as (1) more than one year gap between PD diagnosis and first consultation by a specialist and (2) more than one year gap with no evidence of consultant review. Poor cognition, older age, and worse mobility were strongly associated with suboptimal care. Lower educational level and tremor were moderately associated with suboptimal care.	7
Hemming et al. [78]	USA	The cross-sectional questionnaire was distributed to 1090 PD patients	PD diagnosis confirmed by clinical experts.	2003–2008	1090 patients	Race, income, and educational level.	African American PD patients were less likely to use dopaminergic medications and specially the newer PD medications, prescribed less PD medications, and prescribed more antipsychotics compared with white Americans. Generally, there was no difference between using of PD medications across different levels of incomes and educational levels except that these with lower income or/and low educational level were less likely to be prescribed newer PD medications, and they were more likely to be prescribed antipsychotics.	7
Nyholm et al. [79]	Sweden	Retrospective study that used patients' medical files and national drug registries.	PD cases were confirmed by reviewing medical charts	2006–2007	504 patients	Age and gender	The median levodopa daily dose was 465 mg for men and 395 mg for women. The likelihood of dyskinesia was the same in the patients regardless of their total L-dopa dose. Patients' ages were associated inversely with L-dopa dose.	5
Yacoubian et al. [80]	USA	Retrospective study that used the National Institute of Neurological Disorders and Stroke-sponsored REGARDS study.	Using PD medication consumption as a surrogate for PD diagnosis. No efforts to exclude atypical parkinsonism	2003–2007	190 patients	Gender, race, and health insurance	PD patients without health insurance were less likely to receive PD medications. PD medications use was more common in white Americans than African Americans. PD medications use was more common in men compared with women. There was no association between PD medications use and educational level, income, and geographical residence.	4
Dahodwala et al. [81]	USA	Retrospective study that used Pennsylvania State medicaid claims.	Reimbursement data using ICD-9 code. There were efforts to exclude atypical parkinsonism by excluding patients with history of atypical parkinsonism	1999–2003	307 patients	Age, gender, race, county, and type of prescriber.	African Americans were four times less likely to receive PD medications compared with whites. Older age was associated with not receiving PD medications.	4
Cheng et al. [82]	USA	Retrospective study that used an administrative database (the Network 22 VISN Data Warehouse).	Administrative database using ICD-9 code. No efforts to exclude atypical parkinsonism.	2001–2002	309 patients	Age, race, comorbidity (Charlson index), outpatients' visits, and type of prescriber.	An expert panel has determined multiple indicators for quality of PD care including adding DAs, COMT inhibitors, amantadine, and MAO-b inhibitors if the patient developed wearing-off phenomenon. Adherence to previous quality indicator was more common in non-Hispanic white people than African Americans. Adherence to previous quality indicator was associated positively with a high Charlson index, short time from PD diagnosis, more outpatients' visits, and involvement of movement disorder specialists in patient care.	5