As named plaintiffs in a class action against four companies that allegedly conspired to fraudulently suppress knowledge about the hazards of lead-based paints, Mary Lewis and Tashswan Banks — Medicaid recipients who say the Lead Poisoning Prevention Act, 410 ILCS 45/1, mandated blood screening for their children — struggled with a key ingredient for the underlying tort claim: They had to establish they suffered an economic loss when healthcare providers billed the government for the blood tests.Lewis and Banks didn’t …