i.v. therapy regularly in case of chronic PsA??

Question

Dear Expert Team,

My 11-year-old son contracted PSA 16 months ago (i.v. therapy in June 08 was not successful). Antibodies in serum were positive in April 09. FEV is 92%, and my son is very fit (no secretion, no cough, X-ray negative, good weight).

Is there a recommendation for children to:
- choose the Danish model, or
- do annual prophylaxis with positive antibodies, or
- depending on the clinical condition,
1. (next i.v. therapy at FEV decrease to what percentage? My son does not always blow evenly strong.)
2. would a lung function test every two months or earlier be a compromise???

Many thanks for your assessment.

Answer

Hello,
I am assuming that the questions from April 21 and May 6 were also asked by you, since the specifications about the patient’s age, the time of first PSA evidence, PSA antibodies, and FEV1 value are identical.
You write that Pseudomonas aeruginosa (PSA) was first detected 16 months ago in your 11-year-old son. Two months ago, the annual blood sample showed PSA antibodies for the first time. Therefore, one has to assume a chronic Pseudomonas infection with your son now. All therapeutic measures will therefore have to aim at avoiding structural changes in the lung. In a regular X-ray, early structural changes are often unrecognizable. For that, a computer tomogram (CT) of the lung would be more informative. Lung function does not reliably show early changes either, especially given that the FEV1 values can fluctuate by about 5% even in healthy people. Therefore I would recommend a CT.
Irrespective of this, there is unfortunately no uniform European Consensus on the therapeutic model to use in case of chronic PsA colonization. There is the mentioned danish model which includes apart from a permanent inhalation with antibiotics, regular i.v. antibiotic courses for 14 days (3-4 times a year). These "routine antibiotic courses" are done independently of the clinical situation of the patient. Another model exsits where apart from a permanent inhalation with Tobramycin or Colistin, i.v. antibiotic courses are performed only in case of clinical exacerbation. "Clinical exacerbation" includes findings of decreasing physical working capacity, increasing cough, sputum, decreasing apetite and weight loss, and changes in the FEV1 value in the lung function. Radiological findings in the thorax x-ray or lung CT can also help further defining an exacerbation. Therefore you see that there is no uniform fixed value for the FEV1 as it is not the only criterium which defines an exacerbation which has to be treated with i.v. antibiotics.
Until now there are unfortuntately no prospective, randomised studies with a sufficient number of also jung patients wich have compared both therapeutic strategies.
In summary, there is no "standard model" of treatment for chronic PsA. However, as the results of the Copenhagen CF-center shows a better life expectancy, most centers, and our center as well, perform regular i.v. antibiotic courses in case of a chronic colonization with PsA idependently of the clinicla situation and FEV 1 findings.
Even if we recommend regular intravenous antibiotics therapy (i.v. therapy) every three months, in case of Pseudomonas infection with an FEV1 of 100 %, one can think about extending the intervals between two i.v. therapies. It can be helpful for this decision to do a CT check to see whether the structural changes have increased during therapy.

I hope this information helps.
Kind regards,
Ernst Rietschel

11.08.2009