Analysis of Gluten Free Casein Free Diet

Evaluation of Methods

Sample

Demographic characteristics

The authors had potential biases in the demographics for their study. To start, the authors do not include some demographic information regarding the sampled individuals. They do not report the location or cultural background of any of the individuals. The authors provide no information on the socioeconomic status or educational level of the group participants. In addition, the authors used only 3 girls in this study, versus 12 boys. It is possible that gender can play an important role in diet and autism and future studies by these authors should include a fair gender analysis, if possible, to generalize the results. Although it's not noted in the article, males are 4-5 times more likely than females to have autism according to the DSM-IV-TR, so the sample's ratio of 12 boys: 3 girls is an accurate representation of the DSM's autism prevalence data. It is known that 13 participants completed the study, but the authors neither reveal the gender nor the ethnicity of those participants who withdrew from the study. The individuals are also different ages with a mean age of 7.32, with the youngest age being 2 and the oldest age being 16. The use of this wide range of age can results in a data error. The author does not state if there has been previous research on the differences in autism in age groups of children, especially children undergoing the Gluten-Free and Casein-Free diet. Furthermore, the individuals included in the study were mostly Caucasian, with only one Asian individual; therefore, it is not representative of the entire population. No information about the ethnic composition of the accessible geographical area was provided. The authors do indicate, however, that each individual that was included in the study was based on a diagnosis of an autistic disorder according to DSM IV criteria and according to the score above the cut-off on each symptom domain of the Autism Diagnostic Interview. The authors do not address each individual that was included in the study in regard to their scores according to the DSM IV criteria or the Autism Diagnostic Interview. Therefore, again, it is possible there is a bias and that the sample is not representative of the entire autistic spectrum of diagnosed individuals. Elder et al. did provide information about the clinical profile of the sample. According to Elder et al., inclusion was based on a diagnosis of autistic disorder according to DSM IV criteria and a score above cut-off on each symptom domain of the Autistic Diagnostic Interview Revised (ADI-R) (Elder et. al., p. 415). "Children were excluded from the study if their medical histories and/or physical examinations indicated that they had physical or sensory-impairments or significant medical problems including celiac disease" (Elder et al, p. 416). Although it would have been helpful to have more information on the families attending the center where participants were recruited and more information on the area of Florida where participants were recruited, the information provided is sufficient to describe the sample. Possible limitations include the wide age range of participants, the lack of information on those who withdrew from the study, the absence of additional demographic details, and the lack of detailed information about the diagnostic criteria determined by the ADI-R.

Sample Representative of Population

Since the sample includes only children with ASD, it seems it would be representative but it is not. The sample is fairly representative of the target population's predominant behavioral symptoms. The range of ages (across 16 years) for the small sample seems unsuitable. The accessible/sample population is likely a poor representation of the target population.

Biases evident

Bias is inherent to the nonrandom method of sample selection used. Because they used convenience sampling, limitations can include a potential for generalizing results back to the population could affect the population validity (Houser, p. 139). Lack of resources, time and access to schools may be why Elder et al. limited themselves to a convenience sample. Bias also seems possible due to the relationship between the researcher's university affiliation (University of Florida) and the centers where participants were recruited. Researchers may have had a previous relationship or prior interactions with the participants which has the potential for bias. There is no mention of whether the study's population is representative of the total population.

Sample size:

Elder et al., (2006) did not indicate how they determined the sample size they used during the study. It was noted this was a pilot study, so 15 may have been the number of participants willing to consent to participate. The sample size was only 15, which can cause statistical analysis to have a low power. Therefore, the small sample size in this study could cause sampling error. Still, this is a quantitative study so 15 is sufficiently large. Elder et al., (2006) used children ranging from age 2-16 with a mean age of 7.32 years. This sample size is limited (but still sufficient) for a couple of reasons. For one, the sample size is small. Only 15 children represented a population of autistic children that participate in the Gluten- Free Casein-free Diet. For instance, the sample size in the study described in Elder et al., (2006) conducted by Cade et al., 2000, is 270 individuals. The study hypothesized that schizophrenia is associated with the body's absorption of "exorphins" contained in gluten and casein. Elder et al., (2006) also includes in the paper a study related to GFCF diet in autism where antibodies were measured in 50 children diagnosed with autism. In addition, Elder et al., (2006) proceeds to include Arnold et al., (2003) in which included 26 children with autism on a regular diet, 10 on a gluten and casein free diet and 26 children with developmental delays to serve as controls. In sum, the authors analyzed these previous studies and indicated that the studies did provide information on GFCF dietary effects, but also indicated that the information is limited due to a small sample size. In addition, Elder et al., (2006) states that there needs additional clinical trials due to the previous small sampling size studies; however, their study only includes 15 children, an even smaller sample size than the previous studies indicated. The assumption can be made that Elder et al. accepted those individuals who fit their criteria for the study.

Sampling techniques for the sample

The sample selection was not