Predictive Value: Sickle Cell Anemia in China

By | March 3, 2015

Sickle cell anemia is so rare in China that you would have virtually the same chance of finding sickle cell anemia in these terra cotta soldiers as in a live Chinese person. By Peter Morgan from Nomadic (Detail, Terracotta Warriors) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Sickle cell anemia is so rare in China that you would have virtually the same chance of finding sickle cell anemia in these terra cotta soldiers as in a live Chinese person.
By Peter Morgan from Nomadic (Detail, Terracotta Warriors) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Let us now assume that some overeager field worker from the World Health Organization has gotten a grant to take our easy, cheap, 99% sensitive and 99% specific test for Sickle Cell Anemia and start a screening program in Beijing. The test remains the same but the prevalence of Sickle Cell Trait, not Disease is estimated at 1 per 100,000, which would yield a disease prevalence would be somewhere around 1 in 10 billion or one possible case in the entire country. The good news is that false negatives are not a problem. We will not miss any cases of Sickle Cell Anemia because there aren’t any. The bad news is that 1% of all of the healthy Chinese people 1,000 souls will be erroneously diagnosed with a disease that they couldn’t possibly have. These poor people will have been needlessly worried and the Chinese government will have to administer another test to prove that they are healthy, which we should have known in the beginning. But what you may rightly ask does this have to do with back pain. In our next blog we will apply this type of analysis to a very common problem we see here in Burbank at Schlesinger Pain Centers, the differentiation between axial and radicular low back pain.


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