PEDIATRIC RHEUMATOLOGY UPDATE
Thomas J. A. Lehman MD, Chief
PHONE 212-606-1151 FAX 212-606-1938
EMAIL GOLDSCOUT@AOL.COM ON THE INTERNET HTTP://WWW.GOLDSCOUT.COM
This page is provided by Thomas J. A. Lehman MD
Delivering the best care - with great care
Dr. Lehman is the
author of many textbook chapters and articles on the care of children and young
adults with SLE. He practices in
THE ANA DILEMMA!
A common rheumatic disease related problem faced by pediatricians is the child with a positive test for antinuclear antibodies (ANA). In ‘the old days’ this test was done using a rat liver substrate. A positive test of or greater was meaningful. In general 4% of the population had ‘false positives’ primarily adults. An ANA positive child had a significant risk of rheumatic disease. The problem came from the rat liver substrate. Every time you had to use a ‘new’ rat liver, everything had to be recalibrated. Although positive and negative results were mostly consistent, there was no uniformity in titers between labs. Now most routine laboratories utilize a human cell line (Hep 2 cells) as the substrate. Unfortunately, this didn’t lead to consistency between laboratories. Further, the incidence of ‘false positives’ is much higher. Recent studies have demonstrated as many as 1/3 of healthy adults to be ANA positive at or higher and a similar number of children (refs if you want them)
So we should ignore low titer positive ANAs – right? Well unfortunately some of the people with low titer positive ANAs do have diseases. How does a sensible physician cope? If you go to the textbooks you will read about sensitivity, specificity, positive predictive value, and negative predictive value. These are important to understand for every test we do. Sensitivity – the goal is no false negatives – percentage of those tested with positive tests over number with disease. Does it detect every case? Specificity – the goal is no false positives – percentage of those tested who test negative over number who do not have disease. Positive predictive value – how likely is it that a positive test means you do have the disease. Negative predictive value – how likely is it a negative test means you don’t have disease. An example from the literature* 1010 patients were tested for ANA. 153 were ANA positive, 17 had lupus. Sensitivity 100% - all the patients with SLE were positive. Specificity 86% - 857/1010 tested negative and did not have disease. Positive predictive value was only 11% 17 positive with disease out of 153 positive – oops not so good. Negative predictive value 100% no one who was ANA negative had disease.
Well that’s useful information except for one
thing. The results depend entirely on the population being tested. If you are testing people with symptoms who
you suspect have disease you get entirely different results than if you
randomly test people on the street with no reason to suspect they have
disease. Thus the sensitivity,
specificity, etc all depend on the clinical situation in which the testing is
being done. So is there anything useful
here when you are out in private practice?
General guidelines I use. 1) If
the patient has symptoms of rheumatic disease they should be evaluated no
matter what the ANA result.
2) If the patient has an ANA of or less and no one knows why the test was done there is a good chance it means nothing – but you can’t be sure. If the ANA is 1:80 you are in ‘no man’s land.’ If the ANA is 1:160 or higher, a pediatric rheumatologist should take a look – not all of them will have something, but some will.
Typical example from my practice; a seven year old girl had a recurrent itchy rash. The allergist ordered a panel of tests and the ANA was 1:320. The rash went away. A follow-up ANA was done and was even higher. The girl felt fine, no rash. A few months later another ANA was done which was > 1:320 so she was referred for ‘reassurance.’ CBC, ESR, and Chemistries were all normal, but on full evaluation she turned out to be IgA deficient and have high titer anti-thyroid antibodies and unsuspected mildly symptomatic hypothyroidism.
In the late 70s at Childrens of LA, I had 90 families with children with lupus. I tested every family member and discovered 30 sisters of teenagers with lupus who were themselves ANA positive. Two of these sisters had SLE when examined carefully. I followed the remaining 28, examining them every six months. In two years nothing happened. But by five years 2 had lupus and by ten years 7 did. It would not have been appropriate to start treating any of these sisters until they had diagnosable disease. But ignoring them after the initial negative exam wouldn’t have been right either. Conservative monitoring will prove to have been unnecessary for many, but may save the lives of others. None of us know for sure who is who.
Burke Rehab in
“Dr. Tom Lehman’s experience and compassion are evident on every page of this book, and they help guide the reader—child, parent, and healthcare professional alike – through the world of childhood arthritis. This book is an absolute gem written with a single goal in mind: improve the lives of kids with arthritis.” -- Jack Klippel, M.D. President and CEO of the Arthritis Foundation
“Dr. Lehman has given parents and families of children with
arthritis the first book that speaks to the parent and child as equals. His book explains the illnesses, the
medications, the lab tests, and the disease course in simple, understandable
lay language and givens them valuable insight into how a pediatric
rheumatologist thinks. Bravo!”-- Charles Spencer, M.D.,
Professor of Clinical Pediatrics,
It’s not just
A guide to childhood muscle, bone, and joint pain,
rheumatic diseases and the latest treatments
It has always been a frustration trying to answer the many questions I have received from people over the web. I can’t take the time and give them the detail I would like to. I have to take care of my patients. This book is a distillation of my experience answering questions for parents and health professionals over 25 years of practice. If you want to know about the diseases, the tests, the medications, or how to be sure you are getting the best care– If you are the family member of a child with joint pains, this book will give you the answers. If you are a general physician, a pediatrician, or a nurse who cares for children with these diseases it will answer many of the questions families ask you, and you can recommend it to them. It will also answer many of your questions about what shots to give, what precautions to take, and the other questions families, pediatricians, and other health care providers have asked me over the years.
Dr. Lehman is the author of many textbook chapters and articles on the care of children and young adults with SLE. He practices in New York City. Click here for more information about Dr. Lehman or the Hospital for Special Surgery.
Click here for The Lupus Foundation web page
The Arthritis Foundation also works with children with lupus.
This site provided by Thomas J. A. Lehman MD
Chief, Division of Pediatric Rheumatology
The Hospital for Special Surgery
535 E 70 St,
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