Cunnington AL, White L, Hood K. Identification of possible risk factors for the development of dopamine agonist withdrawal syndrome in Parkinson’s disease. Parkinsonism & Related Disorders 2012;18:1051-52
PubMed link: https://www.ncbi.nlm.nih.gov/pubmed/22677468
| Methods | Study design: Case-control study
Number of groups: Two groups |
| Participants | Number of participants: 46 enrolled
Age: 70 ± 10 years Sex: 15 female, 31 male Participants with dementia: No (median MMSE =29; IQR 28–29.5) Inclusion criteria: · Patients at the clinic · Parkinson’s disease · Dopamine agonist ceased due to adverse effects Exclusion criteria: · Not described Country: Scotland Setting: Community – clinic |
| Interventions | Medicine: Dopamine agonist
Withdrawal Schedule: Taper – not described further |
| Outcomes | Presence of Dopamine Agonist Withdrawal Syndrome |
| Dates | Dates: Not described
Follow-up duration: Not described |
| Funding sources | Not described |
| Notes | Authors stated: “Conflict of interest: The authors declare no conflict of interest.”
Limited detail as it was published as a letter to the editor. |
Risk of bias table
| Bias | Authors’ judgment | Support for judgment |
| Random sequence generation (selection bias) | High risk | Case-controlstudy based on a retrospective review of decisions made in a medical clinic. |
| Allocation concealment (selection bias) | High risk | The two cohorts are those who did and did not experience a specified withdrawal effect (Dopamine Agonist Withdrawal Syndrome). |
| Blinding of participants and personnel (performance bias) | 5 out of 5 | Not a blinded study. |
| Blinding of outcome assessment (detection bias) | 5 out of 5 | As above. |
| Incomplete outcome data (attrition bias) | Unclear risk | It is unclear for there is limited information on which to judge since this paper was published as a letter. |
| Selective reporting (reporting bias) | 5 out of 5 | The study’s outcomes are not explicitly stated. The authors stated that they “wished to review our own experience withdrawing dopamine agonist therapy.” This makes the outcomes appear selective and opportunistic based on the information available retrospectively from patient profiles.
In the introduction, the authors refer specifically to Dopamine Agonist Withdrawal Syndrome. While a number of specific symptoms were included in Dopamine Agonist Withdrawal Syndrome, no method of evaluating Dopamine Agonist Withdrawal Syndrome was given. I could only infer that the method that the authors wished to follow was the occurrence of Dopamine Agonist Withdrawal Syndrome,and this was reported. |
| Confounding (non-randomized) | 5 out of 5 | As a case-control study, the groups are fundamentally unbalanced as they compare those who did experience Dopamine Agonist Withdrawal Syndrome with those who did not.
The protocolwas not pre-specified. However, a number of confounders were reported. |
| Other bias | High risk | Insufficient detail to judge.
A major confounder was not considered,and that was the rate of reduction in dosage. They mention the taper period as being not significant but since there was a significant difference in both total levodopa equivalent daily dose and dopamine-agonist-levodopa equivalent daily dose, the rate of dose reduction should have been included. |
| Newcastle-Ottawa scale | ||
| Selection bias | Is the case definition adequate? | Yes, e.g. record linkage or based on self reports. |
| Representativeness of the cases | Somewhat representative of the average community-based older adults living with Parkinson’s Disease, who are not tolerating dopamine agonist therapy.
Insufficient detail to state if they are truly representative. |
|
| Selection of Controls | Community controls. | |
| Definition of Controls | No report of Dopamine Agonist Withdrawal Syndrome. | |
| Comparability bias | Comparability of cohorts on the basis of the design or analysis | The studycontrols for dopamine agonist withdrawal in an elderly community-based population with Parkinson’s Disease, in whom the medicine had not been tolerated. |
| Outcome bias | Assessment of exposure | Assessment of exposure through record linkage. |
| Same method of ascertainment for cases and controls
|
Yes. | |
| Non-Response rate | Same rate for both groups. | |
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