Genetic test for lactase non-persistence and hydrogen breath test: is genotype better than phenotype to diagnose lactose malabsorption?

BACKGROUND: Adult-type hypolactasia is a widespread condition throughout the world, causing lactose malabsorption. The lactose breath test is a simple tool for diagnosis but the need for prolonged monitoring of hydrogen excretion has led to a genetic test proposal. The aim of this study was to compare the genetic test with the lactose breath test in order to give some insights into the clinical value of genetic testing. METHODS: Thirty-two consecutive functional patients underwent lactose breath test and lactase genetic polymorphism analysis (C/T 13910 and G/A 22018). Intolerance symptoms after lactose load were also monitored. RESULTS: All patients with positive lactose breath test showed homozygosis for both polymorphisms. Among the nine patients with a negative breath test result, six showed heterozygosis while three showed homozygosis. Intolerance symptoms were present in 16 homozygotic patients but also in one heterozygotic patient. The k value for the agreement between the genetic test and the lactose breath test was 0.74. CONCLUSION: A positive genetic test for lactase non-persistence indicates whether lactase activity decline may represent a clinical problem for the patient, but does not give information on actual patient symptoms. On the contrary, this information is already available by combining the lactose breath test with intolerance symptom evaluation. Lactose absorption phenotype may be not yet evident until young adult age.

Visceral hypersensitivity and intolerance symptoms in lactose malabsorption.

Lactose malabsorption is not always associated with intolerance symptoms. The factors responsible for symptom onset are not yet completely known. As differences in visceral sensitivity may play a role in the pathogenesis of functional symptoms, we evaluated whether an alteration of visceral sensitivity is present in subjects with lactose intolerance. Thirty subjects, recruited regardless of whether they were aware of their capacity to absorb lactose, underwent an evaluation of intestinal hydrogen production capacity by lactulose breath test, followed by an evaluation of lactose absorption by hydrogen breath test after lactose administration and subsequently an evaluation of recto-sigmoid sensitivity threshold during fasting and after lactulose administration, to ascertain whether fermentation modifies intestinal sensitivity. The role of differences in gastrointestinal transit was excluded by gastric emptying and mouth-to-caecum transit time by (13)C-octanoic and lactulose breath tests. Lactulose administration induced a significant reduction of discomfort threshold in subjects with lactose intolerance but not in malabsorbers without intolerance symptoms or in subjects with normal lactose absorption. Perception threshold showed no changes after lactulose administration. Severity of symptoms in intolerant subjects was significantly correlated with the reduction of discomfort thresholds. Visceral hypersensitivity should be considered in the induction of intolerance symptoms in subjects with lactose malabsorption.

The role of gastric accommodation in the pathophysiology of functional dyspepsia.

BACKGROUND AND OBJECTIVES: The pathophysiology of functional dyspepsia is not yet completely known. Several mechanisms have been suggested as having a role in symptom onset and impaired gastric accommodation to meal is one of the most frequent. This review will focus on the pathophysiological and clinical aspects of this abnormality. EVIDENCE AND INFORMATION SOURCES: Medical peer-reviewed literature was considered to elucidate the role of gastric accommodation in the pathophysiology of functional dyspepsia. STATE OF THE ART: Impaired gastric accommodation to meal is present in around 40% of patients with functional dyspepsia and it was shown to be associated with the presence of early satiety. Unfortunately, a definitive treatment of this abnormality with fundus-relaxing drugs is not yet available. PERSPECTIVES: Further studies are needed to better clarify the role of each single pathophysiological mechanism on clinical manifestations of functional dyspepsia. Research is still ongoing to offer a valid therapeutic approach.

Experimental study of different intraocular lens designs implanted in the bag after capsulorhexis.

OBJECTIVE: To analyze experimentally in cadaver eyes several models of commercially available posterior chamber intraocular lenses (IOLs) to determine their stability, fixation, and behavior in the capsular bag in relation to their overall size, optic diameter, shape, material, and haptic configuration. SETTING: Eye Bank and Department of Ophthalmology, University General Hospital of Alicante, Spain. METHODS: Thirty-three IOLs of different sizes, shapes, and designs, divided in two series and five groups, were implanted successively in 31 cadaver eyes. All the proceedings were videotaped, and measurements were made on the television screen with the picture static. Main outcome measures were the diameters of the lens, the empty capsular bag, and the capsulorhexis; capsular distension by the IOL haptics; extent of haptic arc of contact with the capsular equator; and IOL mobility in the bag. RESULTS: The stability of and stretching caused by the IOLs varied greatly depending on their overall size, haptic flexibility, and the extent of the arc of haptic contact with the capsular equator. Lenses between 13.5 and 14.0 mm had good stability but stretched the capsule excessively. The J-loop haptic configuration produced a spindle-shaped bag deformity that might come in contact with the ciliary processes in the physiologic eye. Among IOLs designed for in-the-bag implantation after capsulorhexis, the two smaller than 12.0 mm were unstable, permitting excessive mobility in the capsular bag. Except for IOLs with a 5.0 mm optic, all 12.0 mm IOLs had reasonable stability, little or no mobility within the capsular bag, and good short-term centering. Lenses with a broad angulation at the haptic-optic junction, to about 90 degrees, achieved the largest arc of contact with the equator and behaved as lenses with larger optics. The Pharmacia 808 performed best. CONCLUSION: After capsulorhexis and extracapsular cataract extraction, 12.0 mm, poly(methyl methacrylate), one-piece IOLs with modified C-shaped loops, 90 degree angulation at the haptic-optic junction, and an optic diameter between 6.0 and 6.5 mm performed best in the capsular bag.