Overdiagnosis – the word makes no sense

April 13, 2017

In the recent hubbub about the use of PSA to screen for prostate cancer, the word overdiagnosis has appeared several times. In an online dictionary, it is defined as “the diagnosis of a disease more often than it is actually present.”

But the diagnosis of prostate cancer is pretty straightforward, with a biopsy determining whether cancerous cells are present. The diagnosis can be either correct or incorrect. But, there can be overtreatment, when low-risk prostate cancer is treated aggressively. So somehow, overtreatment has spilled over into diagnosis to produce the word overdiagnosis. That is, if a person has a biopsy confirmed prostate cancer, which is low risk and receives aggressive treatment – he has been over treated, not over diagnosed.


Comparison of company vs. standards organization specifications

April 11, 2017

For almost all of my career, I’ve been working to determine performance specifications for assays, including the protocol and data analysis methods to see if performance has been met. This work has been performed mainly for companies but occasionally also for standards groups. There are some big differences.

Within a company, the specifications are very important:

If the product is released too soon, before the required performance has been met, the product may be recalled, patients may suffer harm, and overall the company may suffer financially.

If the product is released too late, the company will definitely suffer financially as “time to market” has been shown in financial models to be a key success factor in achieving profit goals.

Company specifications are built around two main factors – what performance is competitive and how can the company be sure that no patients will be harmed. In my experience this has simply led to two goals – 95% of the differences between the company assay and reference should be within limits which guarantee a competitive assay and no differences should be large enough to cause patient harm (a clinical standard).

Standards groups seem to have a different outlook. Without being overly cynical, the standards adopted are often to guarantee that no company’s assay will fail the specification. Thus, 95% of differences between the assay and reference should be within these limits. There is almost never a mention about larger errors which may cause patient harm.

Thus, it is somewhat ironic that company specifications are usually more difficult to achieve then specifications published by the standards organizations.