Predicting risk of osteoporotic fracture in men and women in England and Wales: prospective derivation and validation of QFractureScores

I read with interest the paper on the prediction of fracture in
England and Wales by Hippisley-Cox and co-workers [1]. There are several
major limitations with the analyses. Risk factors were only assessed at
baseline (e.g. patient’s registration date), not taking into account any
changes in risk factor status over 8 years of follow-up. A patient, who
developed incident cardiovascular disease in the first year of follow-up,
would be incorrectly classified as a patient without for the total
duration of follow-up. Furthermore, it should be well known that GP
medical records record a higher rate of disease in the first year of
registration, reflecting recording of prevalent conditions [2]. In the
analyses by Hippisley-Cox et al, such records would be incorrectly
classified as incident events. In contrast, most researchers would
typically start follow-up, at least one year after registration.

Assessment of risk factors in the time before registration (at baseline),
likely leads to underrecording (e.g., prescriptions are not recorded when
the patient is not registered in the practice). The choice of risk factors
for QFractureScores was inconsistent with literature. As examples, asthma
was selected rather than chronic obstructive pulmonary disease [3,4] (more
prevalent than asthma in elderly). Medical conditions such as dementia and
use of psychotropic drugs such as anticonvulsants, selective serotonin
receptor inhibitors, anxiolytics/hypnotics, and antipsychotics, or the
daily dose of oral glucocorticoids, were not considered. Previous work on
a fracture risk score in GPRD was not discussed [5]. In my opinion, given
these limitations, the application of QFractureScores and its clinical
calculator on www.qfracture.org, should be limited, until these
methodological concerns have been tested.

References

[1] Hippisley-Cox J and Coupland C. Predicting risk of osteoporotic
fracture in men and women in England and Wales: prospective derivation and
validation of QFractureScores. BMJ 2009;339:b4229

[2] Lewis JD, Bilker WB, Weinstein RB, Strom BL. The relationship
between time since registration and measured incidence rates in the
General Practice Research Database. Pharmacoepidemiol Drug Saf.
2005;14(7):443-51.

[3] de Vries F, van Staa TP, Bracke MS, Cooper C, Leufkens HG,
Lammers JW. Severity of obstructive airway disease and risk of
osteoporotic fracture. Eur Respir J. 2005 May;25(5):879-84.

[4] Vestergaard P, Rejnmark L, Mosekilde L, Fracture risk in patients
with chronic lung diseases treated with bronchodilator drugs and inhaled
and oral corticosteroids Chest 2007;132(5):1599-1607

[5] van Staa TP, Geusens P, Kanis JA, Leufkens HG, Gehlbach S, Cooper
C. A simple clinical score for estimating the long-term risk of fracture
in post-menopausal women. QJM. 2006 Oct;99(10):673-82.

Competing interests:
Competing interests:

All authors confirm that they are not involved in any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in this manuscript.

Funding:

The department of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences has received unrestricted funding for pharmacoepidemiological research from GlaxoSmithKline, Novo Nordisk, the private-public funded Top Institute Pharma (www.tipharma.nl, includes cofunding from universities, government, and industry), the Dutch Medicines Evaluation Board, and the Dutch Ministry of Health.