New knowledge and sophisticated diagnostic techniques are helping doctors recognize early signs of autism, Alzheimer"s disease and heart problems in women. Harvard experts report on the advances that are giving patients hope.Early diagnosis of autism is critical because educational programs that build upon a child"s strengths and improve social skills may help sculpt the developing brain, minimizing the impact of the illness later in life. But spotting the disorder is hard since there is no test for it, although scientists are slowly uncovering gene abnormalities that make children vulnerable to autism. Last week The New England Journal of Medicine reported that a specific location on chromosome 16 was the site of mutations responsible for some cases of autism.For now, diagnosis depends on observing a child"s behavior. It"s a complex process, since no two cases are alike and signs range from mild to severe. Indeed, even though signs of autism may be apparent before their first birthday, most children aren"t diagnosed until the age of 3. That makes parents, who are so intimately familiar with their child"s behavior, perhaps the most effective diagnostic "tools". The American Academy of Pediatrics recently issued screening guidelines recommending that pediatricians engage parents in evaluating infants for autism. Even babies developing typically, the guidelines say, should be screened at set intervals, such as during the 9-, 18- and 24-month visits.Alzheimer"s disease, which begins years, even decades, before it causes symptoms, is a quietly ticking time bomb. But until recently doctors had no diagnostic test that could "hear" the ticking. Unfortunately, it didn"t matter much that Alzheimer"s couldn"t be spotted early—at a stage called mild cognitive impairment, or MCI—since there were no treatments. Today, however, there are new diagnostic tests that can detect Alzheimer"s at an early stage, and several disease-modifying drugs are in advanced clinical trials.The brain shrinkage caused by Alzheimer"s can now be measured with volumetric magnetic resonance imaging (MRI). This technique takes a series of MRI brain scans and then uses sophisticated mathematical models to analyze the results. Most important, volumetric MRI enables researchers to identify subtle shrinkage in brain areas first affected by Alzheimer"s, such as the hippocampus, which is involved in memory.Another technology in limited clinical use is fluoro-deoxy-glucose positron emission tomography (FDG-PET). Images produced by FDG-PET reveal patterns of glucose metabolism in the cerebral cortex, the site of abstract thought, reasoning and learning. Because active neurons guzzle glucose for energy, diminished uptake in a specific pattern can denote Alzheimer"s. In the research setting, scientists have even used FDG-PET to identify people who do not yet have Alzheimer"s but are at risk for developing it, or for developing mild cognitive impairment.Although all these new imaging and biochemical developments are individually promising, the combination of several different imaging tests and biochemical markers may yield the most accurate diagnosis. For example, scientists at the New York University School of Medicine have reported that combining volumetric MRI of the hippocampus with spinal-fluid measures improved diagnostic accuracy in identifying people with mild cognitive impairment who are most likely to progress to Alzheimer"s.When it comes to diagnosing the most common kind of heart disease, some cardiologists share Henry Higgins"s lament in "My Fair Lady": "Why can"t a woman be more like a man" That"s because many women don"t have the typical symptoms, like crushing chest pain and shortness of breath brought on by physical activity or stress. Instead, they have diffuse discomfort in the chest, unusual exhaustion or depression without an apparent reason. To make matters worse, the tests considered best at diagnosing coronary-artery disease generally don"t work as well for women as they do for men. As a result, an alarming number of women with heart disease go undiagnosed and untreated despite repeated visits to the doctor and the emergency room.A. because there still exists no test for diagnosis by nowB. because many women don"t have the typical symptoms like men for diagnosisC. the pattern of glucose metabolismD. with volumetric magnetic resonance imagingE. the most efficient technology for diagnosing Alzheimer is combination of different technologiesF. those babies without autism when they start to say single words by 16 monthsG. the symptoms of heart disease often result from cholesterol-filled plaques. Those images produced by FDG-PET can reveal ______.