Nationwide lead tracking efforts might be catching just two out of every three kids with lead poisoning, researchers warn this morning. The CDC’s lead exposure estimates are based on test results provided by doctors. But because testing isn’t mandatory, it hasn’t been clear how many cases those estimates might be missing. So researchers pulled data from a long-running national health survey to offer an alternative count — and the difference was striking. The cases reported to the CDC only accounted for 64 percent of lead-poisoned kids nationwide. In some states, the disparities were even more pronounced: In California, just 37 percent of kids with elevated blood lead levels had been identified. That suggests officials need a new way to keep closer tabs on lead exposures among kids in the US.