Hi Val,
Yes, Dr. Rivkees, of course, does have SWCAH patients that he treats with dexamethasone. According to his paper on dex treatment, "All salt-loosers were also treated with recommended doses of fludrocortisone (0.05 to 0.2 mg/day.") The specific amount, of course, would depend on individual patient needs, but that appears to be the general range, which looks to be not really all that different from the ranges used in treatment with HC. According to Dr. Phyllis Speiser (in talking about HC treatment), "Infants with the salt wasting form of 21-Hydroxylase deficiency require mineralocorticoid (fludrocortisone, usually 0.1–0.2 mg but occasionally up to 0.4 mg daily)......"
If you look at the chart on corticosteroid properties that I sent you last eve, it does look like HC has some salt-retaining properties, while dex has none. At the same time, it has only a minimal amount compared to florinef (a weighted value of 1:125, according to the chart), so if Ashley was still taking florinef during the time that he was on dexamethasone, I would be surprised if the difference in salt-retaining properties between HC and dex was what was responsible for his renin number to go out of whack. Especially since he was on dex for such a short period of time.
Nick is not a salt-waster, so we do not routinely run renin. Dr. Rivkees generally has us do a 24 hr. urine collection, rather than blood tests, anyway. By definition, plasma renin is a blood test, so I am not sure how he measures control in the mineralcorticoid pathway with urine testing. My guess is that he uses more direct tests, such as for aldosterone, sodium, and potassium , which i know you can get from urine, but I am not postitive. We do not see him again till the end of January, but I'll try to remember to ask him, then, if you would like.
I was actually going to suggest that you ask the parents of a couple of his other patients, who frequent this board. One of them is Kaye, so I'm glad to see she beat me to the punch and answered your post herself. Since Kaye's daughter is still an infant, I'm assuming they get blood, rather than urine, tests for her, so Kaye is a far better person than I am to answer the question about frequency of renin testing with dexamethasone treatment.
As far as how to get in touch with Dr. Pang, sorry I really wouldn't know (Geez....I wish I had some sort of clout in the medical community, but have absolutely NONE!!), though I believe she is the CAH medical consultant to MAGIC, so maybe they can give you some ideas. At the same time, while I admire your fearlessness in contacting worldwide medical experts (if only I had half your b***s......LOL!!!), I'm wondering if there isn't an easier way of getting information on recommended tests, as well as frequency of testing. It seems like I come across this information constantly, so will try to pull together whatever I have for you.