Hulda Clark has been criticized because her claims lack scientific validity and consist of anecdotal evidence. Joseph Pizzorno, a prominent naturopathic physician, evaluated Clark's claims and found that her books mixed patients with conventionally diagnosed cancer with those whose cancer diagnosis was based solely on her use of the "Syncrometer". The patients with medically diagnosed cancer did not respond to Clark's treatment, while those she had diagnosed using the "Syncrometer" were "cured". Pizzorno concluded that Clark's treatments were ineffective and treatments based on Clark's recommendations "pose a substantive public health danger".