The comfort and cruelty of statistics, and why I keep licking my daughter.

I enjoyed all of my statistics courses; I understand what statistics mean, and what they don’t mean.  I enjoy talking about them, discussing various approaches and interpretations of statistics. 

And, normally, I take comfort in statistics.  For example, I am terrified of heights, but I love amusement parks and go on every scary roller coaster possible because there is only a 1 in 300,000,000 chance of dying in a roller coaster accident.  Those are good odds, really.

But what I discovered almost immediately upon becoming a parent was that the margin of error I am comfortable with decreased by about 50 logs when it comes to my children.

Today I got one of the worst phone calls of my life – it was from our pediatrician.  She said one of the newborn screens came back positive for Lily.  One of the bad ones – cystic fibrosis.  This doesn’t mean that she has cystic fibrosis, necessarily.

Lily’s IRT levels were elevated, which is a risk factor for CF.  Because this screen came up positive, they did a DNA test, and found that she has at least one mutation in the CF gene.  If they had found two mutations, she would very likely have CF.  Usually (here is where statistics play an ugly and terrifying game) babies with elevated IRT levels and one known mutation are healthy carriers of the gene.  In this case, Lily would not develop CF, but her children would have a chance of developing CF if she married somebody who was also a carrier. 

But … she could have CF.  The screens are designed to test for only the most common CF mutations, and there are thousands.  The “odds” of her testing positive for CF at this point are approximately 1 in 30.  Lower than 5%.  These are good odds, says my pediatrician.  But 5% is, statistically speaking, an impossibly enormous number if you are a mother waiting to find out if your child’s life could be characterized by pain and suffering and hospitals and loneliness.

Wednesday we will have a sweat test done – to see if there is too much salt in her sweat (apparently one of the first symptoms is salty-tasting sweat).  It might be too early to tell, just to warn you.   All these medical and scientific advancements, and the diagnosis of one of the world’s most devastating illnesses comes down to salty sweat.  Huh.

Lily “probably” doesn’t have cystic fibrosis: http://www.bcwomens.ca/NR/rdonlyres/776E6BBA-747A-4D9C-8447-15603FE49955/42627/CysticFibrosis1mutation3.pdf

This morning when I woke up, I was worried about whether I was going to get the laundry done.  The laundry, for the love.  How could that possibly have mattered?

When it comes down to it, the statistical prognostic seems meaningless.  She either has CF or she doesn’t.  It’s 50/50 from where I stand, and where I stand feels like the unstable edge of the highest, pointiest precipice on earth, with a blizzard on the horizon with a 1:30 chance of heading my way.

……………..

After I spoke with the pediatrician and a doctor in the pulmonary center at Children’s Hospital about her sweat test, I fed Lily, and begged her not to test positive.  Instead of answering, she fell asleep.  I put her down for a nap, but then decided the laundry could wait.  I picked her up and lay her on my chest while I watched her sleep, happy that she was blissfully unaware that little tear drops kept falling on her head.