Bone Abstracts

Teriparatide is an anabolic agent given to reduce fracture risk in osteoporosis; it increases BMD and bone turnover. For monitoring treatment efficacy, serum PINP shows the greatest increase and low variability; it has been proposed as a marker of individual treatment response. We aimed to evaluate the utility of PINP to monitor teriparatide treatment in clinical practice.

We performed a retrospective evaluation of 91 patients treated with teriparatide since PINP (Elecsys) was introduced in our centre in 2009 (81 women, mean age 71 (48–92) years, mean 5 vertebral fractures (0–13)). Lumbar spine (LS) BMD was considered uninterpretable in 47 patients due to artefacts in the region of interest (vertebral fractures, degenerative change). At baseline, mean±S.D. BMD T-scores at LS (reliable scans only) and total hip (TH) were −3.0±1.0 and −2.3±1.2 respectively; mean PINP was 35±29 μg/l (5–161). Treatment response was defined as either an increase in PINP greater than the least significant change (LSC, >10 μg/l), or an increase above the premenopausal reference range (>80 μg/l).

At 3 months, 69/74 patients (93%) were defined as responders using the LSC approach and 49/85 (58%) using the absolute threshold. 40/74 (54%) patients fulfilled both criteria. Of 44 patients with reliable LSBMD at baseline, 16 had 24-month follow up, of whom 88% were defined as responders (BMD LSC, 4.5%). For THBMD, 49 had 24-month follow up, of whom 22% were defined as responders. There was no association (r=−0.002, NS) between 3-month PINP change and 24-month LSBMD change.

In summary, PINP identified a similar proportion of responders to teriparatide treatment in clinical practice as reported in clinical trials (using LSC criteria). LSBMD measurement was uninterpretable in many patients and early change in PINP did not predict change in LSBMD. We conclude that PINP has greater utility than BMD in monitoring individuals treated with teriparatide in clinical practice.