Diagnosis of lactose intolerance and the "nocebo" effect: the role of negative expectations.
BACKGROUND
Diagnosis of lactose intolerance is based on a "positive" H(2) breath test associated with abdominal symptoms. The present study established to what extent the occurrence of symptoms during a "negative" H(2) breath test may result from a "nocebo effect" instead of lack of sensitivity of the procedure.


METHODS
Between 2005 and 2007, 636 outpatients performed a standard 4-h 25g lactose tolerance test. The test was positive in 254, negative in 325, and 57 patients were H(2) "non-producers". Twenty-seven patients reporting symptoms despite a negative H(2) breath test underwent a "sham" breath test following ingestion of 1g of glucose. Fifty-four patients presenting with documented lactose intolerance were used as controls.


RESULTS
Twelve out of 27 patients (44.4%), and unexpectedly also 14 (25.9%) controls presented abdominal symptoms during the sham test. The difference between the two groups was not significant (P<0.15) OR 2.28; C.I. 0.77-6.78.


CONCLUSIONS
In most instances, symptoms reported by patients during a negative lactose H(2)BT cannot be attributed to a false-negative test. Instead, a non-organic component, resulting from negative expectations ("nocebo effect") is likely implicated. Moreover, also in patients diagnosed as lactose intolerant, the need for restricting the primary source of dietary calcium should be critically reconsidered.
Vernia
Piero
P
Gastroenterologia A, Dipartimento di Scienze Cliniche, Sapienza Università di Roma, Viale del Policlinico, 00161 Roma, Italy. vernia@uniroma1.it
Di Camillo
Mauro
M
Foglietta
Tiziana
T
Avallone
Veronica E
VE
De Carolis
Aurora
A
D000328:Adult; D000368:Aged; D001944:Breath Tests / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D007787:Lactose Intolerance / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D055815:Young Adult
D006859:Hydrogen