Calculating your own results

The doubly-labelled water calculations for both human and animal applications can be made using a specialised program that was written by Cliff Lemen (Natureware Ltd) to my specifications, and funded by the UK NERC scientific services section.

The main advantage of this program is that it perfoms an iterative calculation systematically deleting and reinserting individual values into the calculation (see Speakman, JR 1995   Estimation of precision in DLW studies using the two-point methodology. Obesity Research 3 (Supplement 1: 'Recent advances in the doubly labeled water technique' Eds. Speakman J.R. and Roberts, S.B.) for more technical details.).

The advantage of this approach is an estimate can be derived of the analytical precision of the derived mean estimate. This is particularly useful for (a) detecting outliers that have low analytical precision or (b) weighting analyses by the precision of the measurement.

The downside of the program is that each data item needs entered individually and each individual is calculated separately. For some calculations that rely on group estimates of dilution spaces this means everything has to be entered into the program twice. However, this is the only program available that makes the precision estimates.

The program can be downloaded free of charge here.

The only condition of use of the program is that its use is acknowledged in any publication. A suitable reference is

Speakman, J.R. and Lemen, C (1999) DLW analysis program. Natureware Ltd. Downloaded from labelled water/program

We have produced a userguide for the program which can be downloaded free here.

The UK company iso-analytical have produced an independent userguide for the program which is a bit more user friendly than ours. Their userguide was authored by V.R. Nevolo (2003) and can be downloaded free here. Note this userguide is actually an application note on how to use the method and send samples for analysis to their laboratory. The details of how to use the DLW program are on the last few pages of the note.