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(also known as array genomic comparative hybridization, or array CGH) with established diagnostic procedures including G-banded karyotype and fragile X testing. Arrays for CMA tests are widely available, but have not yet entered general practice to the extent that generally agreed standards and references exist. Applying CMA to the entire genomes of 697 ASD patients, Shen et al. detected clinically relevant CNVs in 51 individuals (7.3%). Targeting the method at the most promising genomic regions with a smaller group of patients, they only had a discovery rate of 5.3%, but in both cases the yields are much higher than for established chromosomal tests. These authors conclude that “CMA had the highest detection rate among clinically available genetic tests for patients with ASD”. Therefore, they recommend, “CMA should be considered as part of the initial diagnostic evaluation of patients with ASD”. The International Standard Cytogenomic Array (ISCA) consortium conducted a literature review and came to the same conclusion (Am. J. Hum. Genet. (2010) 86, 749). Still, the analysis by Shen et al. detected clinically relevant CNVs in only 7.3% of the ASD patients tested, and the specific significance of those found remains uncertain. As none of the diagnostic results suggests any treatment options, there is no immediate benefit to the patients. They may benefit indirectly in the long term, as more data accumulate and scientists gain a better understanding. Patients’ families may benefit from finding out whether the specific case is associated with a de novo event or an inherited variation, which can drastically change the recurrence risk for future offspring of both the parents and unaffected siblings. Clinical testing may in the long term also help to clarify the boundaries of the autistic spectrum and get a more reliable measure of its prevalence. An indication regarding the extent to which these issues are still in flow has emerged recently with a study conducted in South Korea which claimed a surprisingly high prevalence of ASD of 2.64% (3.74% for boys and 1.47% for girls), based on a screening of over 55,000 children aged 7 to 12 (Am. J. Psychiatry, doi: 10.1176/appi. ajp.2011.10101532). Young Shin Kim and co-workers at Yale went through a case identification process involving several steps and addressing the entire population of 7to 12-year-olds in the community they studied. An initial screening covering both regular schools and special-needs schools yielded around 2,000 potential candidates, of whom 286 were assessed for ASD. Of these assessments, 201 returned a positive diagnosis for ASD. As there were inevitable losses along the way of families who didn’t respond or failed to consent to the assessment, the authors have had to use statistical extrapolation to arrive at the reported prevalence rates. Beyond statistical uncertainties, these findings raise all kinds of questions as to where to draw the line between ASD and ‘normal’, whether the condition is still widely underdiagnosed, and whether prevalence is still increasing. Nearly seventy years after Leo Kanner first recognised and described autism, its scientific understanding is still very much at the beginning.