Discrimination between maximal and submaximal effort in lumbar dynamometry

Illness deception and work: incidence, manifestations and detection

BACKGROUND

Illness deception (ID) may be difficult to detect. Objective techniques that improve a doctor's skills of detection will have benefits for the health economy.

AIMS

To ascertain the incidence of ID in a general occupational medicine clinic, to give examples by way of case vignettes how it may manifest and to compare the variability of maximal grip strength measurements of patients with suspected simulated weakness of grip with controls.

METHODS

Four hundred consecutive new patient referrals were examined by the author and those who met Diagnostic and Statistical Manual-IV criteria for factitious disorder (FD) or malingering identified. Those with suspected simulated weakness of grip were asked to perform three consecutive maximal grips with a Jamar hand dynamometer. One hundred normal subjects and 100 patients with rheumatoid arthritis (RA) of the hands were similarly tested.

RESULTS

Thirty-two of 400 (8%) patients exhibited behaviour in keeping with ID (29 malingering and 3 FD). Cases included simulated hand-arm vibration syndrome, occupational asthma, deafness and weakness of a limb. The median and 90th percentile for coefficient of variation (CV) of three consecutive maximal grip strengths for normal subjects and patients with RA were 5.2, 10.5%; 5.4, 14.5% right and 4.5, 10.2%; 6.0, 14.4% left hand, respectively. The CV of the six patients who simulated weakness of grip was from 17.3 to 37.8%.

CONCLUSIONS

ID is relatively common in occupational medical practice and multiform in its manifestations. Simulated weakness of grip should be suspected when consecutive declared maximal grip strengths are inexplicably submaximal for age and sex and highly variable in force.