Regression discontinuity

In the cut-off trial there are then three regions for allocation. If the middle randomized region is eliminated so that the two outer regions meet, we then have the extreme example of a cut-off design, the regression discontinuity design. In analysing the cut-off... 

For a=0, which corresponds to the extreme case of a cut-off design in which no patients are randomized (the regression discontinuity design), E[A2 2.75. For a = oo we have a completely randomized design and A2 1. 

Credible evaluation uses robust statistical techniques to construct the counterfactual. These techniques include randomization or experimental design quasi-experiments such as matching, regression discontinuity design, or double differences and nonexperimental or instrumental variable methods (annex 6.3). All these techniques try to guarantee the comparability of the treatment and control groups by avoiding what statisticians refer to as bias (box 6.7). 

Lemieux, Thomas, and Kevin Milligan. 2008. Incentive Effects of Social Assistance A Regression Discontinuity Approach. 142 (2) 807-28. 

Woutersen RA, Eeron VJ Inhalation toxicity of acetaldehyde in rats. IV. Progression and regression of nasal lesions after discontinuation of exposure. Toxicology 47 295-305, 1987... 

Lupus erythematosus Hydralazine may produce a clinical picture simulating systemic lupus erythematosus including glomerulonephritis. Symptoms usually regress when the drug is discontinued, but residual effects have been detected years later. Long-term treatment with steroids may be necessary. 

Malignant lymphomas Malignant lymphomas, which may regress following withdrawal of methotrexate, may occur in patients receiving low-dose methotrexate and, thus, may not require cytotoxic treatment. Discontinue methotrexate first and, if the lymphoma does not regress, institute appropriate treatment. 

Photosensitization occurs in 10% of patients. With continued treatment, the skin assumes a blue-gray coloration. The risk is increased in patients of fair complexion. The discoloration of the skin regresses slowly, if at all, after discontinuation of amiodarone. 

G. Other applications Goserelin is useful for in vitro fertilization and is possibly effective in controlling precocious puberty and early puberty. Goserelin may promote fibroid regression, but rapid regrowth results upon discontinuation. 

In this light, Robinson et al. (206) performed a study of 104 first-episode patients who were followed for a minimum of 2 months (mean, 207 weeks). The protocol was later limited to a maximal 5-year follow-up. Patients who wished to discontinue drug could do so. The rate of relapse was determined by the Cox Proportional Hazard Regression model. The cumulative life table relapse rate at 5 years was 82%. Most importantly, despite use of medication by many, there were only four unrelapsed patients after 5 years. Although medication was not controlled, the patients who discontinued had a fivefold increase in the relapse rate. This finding suggests that almost all first admission patients will relapse within the next 5 years, suggesting that most should be on maintenance medication. 

Tebbe B, Mayer-da-Silva A, Garbe C, von Keyserlingk HJ, Orfanos CE. Genetically determined coincidence of Kaposi sarcoma and psoriasis in an HIV-negative patient after prednisolone treatment. Spontaneous regression 8 months after discontinuing therapy. Int J Dermatol 1991 30(2) 114—20. 

Buhler H, Pirovino M, Akobiantz A, Altorfer J, Weitzel M, Maranta E, Schmid M. Regression of liver cell adenoma. A follow-up study of three consecutive patients after discontinuation of oral contraceptive use. Gastroenterology 1982 82(4) 775-82. 

Marks WH, Thompson N, Appleman H. Failure of hepatic adenomas (HCA) to regress after discontinuance of oral contraceptives. An association with focal nodular hyperplasia (FNH) and uterine leiomyoma. Ann Surg 1988 208(2) 190-5. 

Figure 7.23. Effects of temperature on mitochondrial function. (Upper panel). Arrhenius plot illustrating the slope discontinuity ( break ) that commonly occurs at a high temperature of measurement, the Arrhenius break temperature (ABT). Data are for mitochondria of the hydrothermal vent tubeworm Riftia pachyptila (after Dahlhoff et al., 1991). (Lower panel) Arrhenius break temperatures for mitochondrial respiration of diverse invertebrates and fishes. The open square is for mitochondrial respiration of the Antarctic nototheniid fish Trematomus bernacchii and is not included in the regression analysis. A line of identify (ABT = adaptation temperature) is also shown (see text for analysis). (Data from Dahlhoff and Somero, 1993b Dahlhoff et ah, 1991 Weinstein and Somero, 1998.)...

A 55-year-old man with a 15-year history of schizophrenia treated with various neuroleptic drugs developed a tremor and was given tetrabenazine 75 mg/day, with complete regression of the tremor. Three months later he developed depression, a known adverse effect of tetrabenazine, which was discontinued, with subsequent partial improvement of his depressive symptoms but reappearance of the tardive tremor. Clozapine 25 mg/day was started and increased to 75 mg/day his tardive tremor again disappeared. 

CMV retinitis is the most common opportunistic eye infection in patients with AIDS and immunocompromised transplant patients. Antiviral medications used in the treatment of CMV are generally administered in two stages induction therapy, to achieve disease regression, followed by maintenance therapy. The incidence of CMV retinitis has decreased significantly with the advent of HAART for AIDS, and antiviral therapy for CMV may often be discontinued in patients who respond favorably to HAART and achieve an elevation in CD4 cell levels above lOO/pl. Refer to Chapter 32 fiar the drug treatment of ocular CMV infections. 

Proptosis, as an isolated finding, rarely requires treatment unless there is secondary exposure keratopathy or unless it represents a significant cosmetic problem. Affected patients may benefit from a trial of systemic corticosteroids. A significant decrease in the severity of proptosis may be observed in some patients. In general, if regression of the proptosis occurs after the institution of steroid therapy, it will begin soon after the onset of therapy and reach a maximum in 2 or 3 months. If no response to steroid therapy is seen after 3 to 4 weeks, the therapy should be discontinued. As mentioned previously, response to corticosteroid therapy for proptosis is variable at best. 

The most important difference between high-dose and low-dose toxicity is the extent of reversibility after discontinuing the drug. Patients taking 20 mg twice daily may demonstrate regression of retinopathy and improvement in visual symptoms. 

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