未熟児網膜症の発症因子の統計学的解析

Statistical analysis of causative factors in retinopathy of prematurity

　旭中央病院新生児医療センターで管理された出生体重2,500g未満の低出生体重児239例を対象とし，多重ロジスティック回帰分析を用いて未熟児網膜症（ROP）発症に影響すると考えられている16因子を検討し，発症の予測を行った。発症に関与する因子は出生体重，酸素投与期間，在胎期間，人工換気日数，酸素投与最高濃度，人工換気の有無，気管支肺異形成，Apgar score 1分値，動脈血酸素分圧（PaO₂）が60 mmHg未満の時間，PaO₂の平均，呼吸窮迫症候群，PaO₂が60mmHg未満かつ80 mmHg以上の時間の12因子であった（P＜0.05）。多重ロジスティックモデルの変数選択によって出生体重（W）とApgar　score 1分値（A）が選択され，次式が発症確率の予測式として求まった。

　P=1／1＋exp （-λ）

　λ=9.462-0.005553×W-O.3604×A

　このモデルにより，出生直後から効率よく発症を予測することができ，ROPの予防，予後の管理に役立つと考えられた。

We performed a prospective study to evaluate the incidence of retinopathy of prematurity (ROP) in inborn infants of less than 2,500 g at birth. Two hundred thirty nine infants were eligible for this study. We selected a total of 16 risk factors which might influence the incidence. We analyzed the data using multiple logistic regression analysis. The following twelve factors were statistically significant variables to cause ROP by chi-square test (in the increasing order of p-valve), birth weight, duration of oxygen supply, gestational period, duration of assisted ventilation, maximum concentration of oxygen, with or without assisted ventilation, broncho-pulmonary-dysplasia, Apgar score at 1 minute, the number of times that arterial oxygen partial pressure (PaO₂) was below 60 mmHg, average of PaO₂, respiratory-distress-syn-drome and the number of times that PaO₂ was less than 60 mmHg and greater than 80 mmHg (p<0. 05). Birth weight (W) and Apgar score at 1 minute (A) were selected to be independently causative factors of ROP by step wise regression. The logistic model to predict the incidence of ROP was expres-sed in the following equation

P=1/1+exp (-λ)

λ= 9.462-0.005553×W-0.3604×A

When the value for P was 0.27, sensitivity was 80. 5%and specificity was 91.6%.

It was concluded that this model is useful to predict an incidence of ROP at birth.