自閉症與極早產有關
作者：Caroline Cassels出處：WebMD醫學新聞
February 10, 2009 — 新研究結果顯示，每5位早產超過3個月的兒童中，就有1位在2歲時自閉症異常（ASD）篩檢呈陽性。
這項最新的研究結果是來自極低年齡新生兒（ELGAN）研究，研究顯示，這些兒童中，21%在24個月時的兒童修正後自閉症查檢表（M-CHAT）篩檢呈陽性；在排除沒有運動、視覺、聽覺、或是認知受損後，10%篩檢結果為陽性。
在未經選擇的16至30個月的兒童中，研究已經證實在常規的兒童照護訪視中，5.7%自閉症篩檢陽性。
主要研究者、來自麻州波士頓大學的Karl C. K. Kuban醫師在一項聲明中表示，早產超過3個月的兒童，經由M-CHAT篩檢呈陽性的機率明顯高出兩倍。
研究者們也發現罹患小兒麻痺的兒童中將近一半，以及視覺或視聽覺受損的兒童中將近三分之二，其M-CHAT篩檢都是呈陽性的。
這項研究線上發表在1月28日的小兒醫學期刊上。
【期望機率加倍】
這項研究針對於2002年到2004年之間出生，參與ELGAN研究的988位兒童，這是一項大型多中心研究，目的在檢驗懷孕週數少於28週出生兒童的結構與神經功能。
大約在24個月時，研究受試者接受一項完整的發育評估，包括神經學檢查、整體運動功能分類系統（GMFCS）評估、Bayley嬰兒發育指數、BSID-II第二版評估、以及許多雙親進行的評估，包括M-CHAT。
研究者們接著比較小兒痲痺兒童、認知功能受損、視覺或聽覺功能受損兒童M-CHAT陽性機率，以及那些被篩檢有ASD但沒有這些缺陷的兒童。
在整個研究組中，212位（21%）以M-CHAT篩檢呈ASD陽性。在沒有運動、視覺、或是認知功能異常的兒童中，10%篩檢呈陽性。
作者們表示，重大運動、認知、視覺與聽覺受損顯然解釋了超過一半極低懷孕週數新生兒M-CHAT篩檢陽性的原因。即使在排除這些缺陷後，10%兒童篩檢結果呈陽性，將近超過預期的一倍。
【需要修改篩檢工具？】
然而，研究者們附帶表示，雖然有運動、視覺或是聽覺受損的兒童比較可能是M-CHAT篩檢陽性的，目前仍不清楚這些兒童的自閉症風險是否真的較高，或是他們並存的缺陷僅與自閉症常見的特徵相符。
研究者們表示，這有一種可能性，在目前這個形式下，M-CHAT的專一性對於極早產兒童來說是很低的，且這可能需要針對這個族群病患進行修改。
在隨後的主編評論中，來自於英國倫敦學院的Neil Marlow醫師與Samantha Johnson博士指出，因為早期確認可以讓我們早期治療ASD兒童，因此篩檢被設計成過度偵測處於風險的兒童。
他們寫到，相對的，這項研究結果喚起了我們對於闡釋臨床或研究目的篩檢結果的議題；最終，我們將必須進行長期以及臨床診斷，好讓我們進一步了解這個症狀在早產族群的重要性。
研究者們表示沒有相關資金上的往來。
Autism Linked to Very Premature Birth
By Caroline Cassels
Medscape Medical News
February 10, 2009 — New research shows that 1 in 5 children born more than 3 months premature screens positive for autism spectrum disorder (ASD) by age 2.
The latest findings, from the Extremely Low Gestational Age Newborns (ELGAN) study, show that 21% of such children screen positive on the Modified Checklist for Autism in Toddlers (M-CHAT) at 24 months. But after excluding children without motor, vision, hearing, or cognitive impairments, 10% screened positive for symptoms of the disorder.
In unselected children aged 16 to 30 months, research has shown that 5.7% screen positive for autism during routine well-child-care visits.
"Children who are born more than 3 months premature appear to be twice as likely to screen positive on the M-CHAT," principal investigator Karl C.K. Kuban, MD, from Boston University, in Massachusetts, said in a statement.
Investigators also found that nearly half of the children with cerebral palsy and more than two thirds of those with visual or hearing impairments screened positive on the M-CHAT.
The study was published online January 28 in the Journal of Pediatrics.
Doubling of Expected Rate
The study looked at 988 children born between 2002 and 2004 who were participants in the ELGAN study, a large multicenter study that is examining structural and neurologic outcomes in infants born at less than 28 weeks' gestation.
At approximately 24 months of age, study participants underwent a complete developmental assessment, which included a neurologic examination; a Gross Motor Functional Classification System (GMFCS) assessment; a Bayley Scales of Infant Development, 2nd edition (BSID-II) assessment; and several parent-reported assessments, including the M-CHAT.
Investigators then compared the M-CHAT-positive rate of children with cerebral palsy, cognitive impairment, and vision and hearing impairments to the rate of those who screened positive for ASD but who did not have such deficits.
Of the total study group, 212 (21%) screened positive for ASD on the M-CHAT. Among children without motor, visual, hearing, or cognitive impairments, 10% were positive for ASD.
"Major motor, cognitive, visual, and hearing impairments appear to account for more than half of the positive M-CHAT screens in extremely low-gestational-age newborns. Even after those with such impairments were eliminated, 10% of children — nearly double the expected rate — screened positive," the authors write.
Need to Modify Screening Tool?
However, the researchers add that although children with motor, vision, or hearing impairments were more likely than others to score positive on the M-CHAT, it is not yet known whether these children are really at increased risk for autism or whether their existing deficits are simply equated with characteristics commonly seen in autism.
This raises the possibility, say the researchers, that in its present form, the specificity of the M-CHAT could be low in very premature children, and that it might need to be modified for use in this patient population.
In an accompanying editorial, Neil Marlow, MD, and Samantha Johnson, PhD, both from University College London, in the United Kingdom, point out that because early identification leads to early treatment of children with ASD, screening tests are designed to overidentify children at risk.
The study's findings, they write, highlight the pitfalls of screening for autism in impaired populations. However, they add, the results do not negate the need for early screening.
Rather, they say, the findings "raise our awareness of issues involved in interpreting screening results both clinically and for research purposes. Ultimately, we will need to look longer term and to clinical diagnoses to enable us to understand better the significance of such symptoms in preterm populations."
The researchers have disclosed no relevant financial relationships.
J Pediatr. Published online before print January 28, 2009.
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