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symptomatic improvement.

Surprisingly, one metaanalysis found that the placebo response declined significantly as the number of office visits increased, and that each visit was associated with a 4.4% reduction in placebo response rate.136 Noting that this finding is counterintuitive, the investigators hypothesized that increased interaction with an investigator who is not the patient's primary doctor may have a negative effect, a greater number of office visits may be associated with inadequate blinding, and extra visits provide patients who are obtaining insufficient relief with study medication with increased opportunities for expressing their disappointment.136 This analysis also found a significantly lower placebo response rate in clinical trials that used the stringent Rome I or II diagnostic criteria as an entry criterion compared with studies that used the more permissive Manning or other unspecified criteria.136 Use of the Rome criteria may lead to a lower placebo response because it results in a more homogeneous population with a confirmed diagnosis of IBS.136

IBS is a disorder of GI motility and sensory disturbance, and assessment of efficacy is complicated by the absence of physiological markers and the variability of symptoms.137,138 A major difficulty in trial design has been defining endpoints that will represent appropriate measures of efficacy.132,133,139,140 Many authorities favor the use of a global assessment as the primary efficacy measure in IBS studies, but there is widespread disagreement about the type of global assessment that should be used.132,138-141

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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