Confirmatory Bioassay Program

DOE-STD-1121-98

declaration, with a follow-up special bioassay at the conclusion of pregnancy if the worker continues to

be exposed to possible intakes. Sikov and Hui (Sikov et al. 1996) provide methods for embryo-fetus

internal dosimetry.

5.7 CONFIRMATORY BIOASSAY PROGRAM

A confirmatory bioassay program involves limited surveillance of workers to provide verification

that routine bioassay is not required. As described by ICRP Publication 54 (ICRP 1988), confirmatory

monitoring programs are qualitatively useful to show that results are as expected. Any unexpected results

warrant special investigation and may suggest the need for a routine monitoring program. A confirmatory

bioassay program for a work group having low potential for significant intake may involve sampling a

small fraction (e.g., 10%) of the group at a relatively constant rate over a 1-year period. Confirmatory

bioassay programs should not be interpreted in terms of minimum detectable dose. This type of program

is particularly suited for radionuclides which are easily detected at low levels relative to levels of concern.

5.8 TIMELY RECEIPT OF BIOASSAY RESULTS

Bioassay measurement results should be provided in a manner timely to the purpose for which they

are obtained. Factors to consider in determining timeliness include:

use of results to implement or determine efficacy of dose reduction therapy

use of results for preliminary assessments for rapid reporting to the worker and management and for

determining appropriate follow-up activities

need to confirm a suspected intake based on a high routine measurement before detection capability

is lost due to normal biokinetics

trade-offs in sensitivity (due to analytical short-cuts and reduced counting times) for rapid results.

Because in vivo measurement data is usually available almost immediately upon completion of the

measurement, the response times discussed in this section will generally apply to excreta bioassay

measurements.

Confirmatory bioassay measurements are not expected to show any significant detection of nuclides

of concern. Since the purpose of these measurements is merely to provide general information that

significant intakes are not occurring and that radiological controls are effective, the time between

obtaining a bioassay sample (or measurement) and receipt of the results need not be rapid. Likewise,

where routine periodic measurements are not likely to show significant intakes with regard to dose control

and work administration, a 1- or 2-month analytical response time is not likely to have any significant

impact. Generally speaking, a 1-month turnaround time for routine excreta sample analysis does not pose

serious problems for either analytical laboratories or worker monitoring programs.

Special bioassay measurements should have much faster response time. This is particularly

important if the results are being used to determine need for, or efficacy of, dose reduction therapy.

Rapid availability of special results is also needed for preliminary intake and dose assessments used to

classify intakes for reporting purposes. It is suggested that some kind of preliminary bioassay

measurements should be available within 24 to 48 hours following intake. The need for precision and