neonatal screening result

Question

Hello! My daughter is 5 week and 2 days old at the time that I’m writing you. At the neonatal screening, the value of immunoreactive trypsin was 64.9, and at the age of 4 weeks and a half, we repeated the analysis and the value was 1024 (400 being the maximum for that age). In both cases the blood draw was made at Euroclinic, and the analysis was made by SYNLAB in Germany. By now, the weight gain was of 870 grams, she has good appetite, the stool is normal, a few times a day and the smell is not that unbearable. From time to time she has nasal secretions but they are quite compact, and I think it’s because of the humidity level of the room which is low enough. I have to purchase a room humidifier. She doesn’t sweat very much and her skin isn’t salty. Is it possible that these tests are wrong? I mention the fact that there are no cases of CF in our families. We continue the investigations, but we would like an approved opinion about these test results. Thank you and I am waiting an answer from you.

Answer

Hello,
The immunoreactive trypsin test is first performed in the first days of life (until day 5). If the values exceed a certain cut-off value (which differs from laboratory to laboratory) the test is positive, and a second IRT testing at the age of 3-4 weeks is performed like in your case. If this is again positive, this is highly suspicious for CF and therefore other tests are MANDATORY, like sweat test and/or genetic test. The fact that there are no cases of CF in your families is not relevant. CF is a disease in which the incidence of heterozygotes (carriers) is very high. In conclusion somme more test, like mentioned could clarify the probleme. If you need any help, please let us know.
Sincerely yours,
Prof.Dr.Liviu Pop

26.05.2011