Helicobacter pylori infection in Arctic Indigenous communities: assessing the validity of infection status measures and estimating the effect of bacterial load on gastritis severity
Notice bibliographique
Résumé
Helicobacter pylori (Hp) causes chronic inflammation of the stomach lining, also known as gastritis, in nearly all people with a persistent infection. Chronic inflammation of the stomach lining can lead to atrophy of stomach glands, a condition known as atrophic gastritis, believed to be the start of a sequence of pathological conditions associated with an increased risk of stomach cancer. The Canadian North Helicobacter pylori (CANHelp) Working Group conducted community projects to respond to concerns of Arctic Indigenous communities about health risks from Helicobacter pylori (Hp) infection. CANHelp community projects used multiple methods for classifying Hp infection, including the urea breath test (UBT), pathological evaluation of stomach tissue, and tissue culture. My thesis assessed the validity of Hp infection detection methods and estimated the effect of the Hp bacterial load on the severity of gastritis among CANHelp project participants. Estimating the accuracy of alternative staining methods provides information needed to evaluate the cost-effectiveness of special stains for detecting Hp. In this thesis, I investigated whether using special stains (Giemsa, Warthin-Starry and/or immunohistochemical (IHC) stains) on tissue slides for pathological assessment of stomach tissue biopsies improves the accuracy of Hp detection. To do this, I analyzed data from participants with stomach tissue biopsies collected from 2008 through 2013 in 4 CANHelp community projects. I estimated accuracy measures (agreement, sensitivity, specificity, and predictive values) for each stain’s classification of tissue samples as Hp-positive or Hp-negative compared against different definitions of the ‘gold standard’ classification. I also compared the Hp density gradings of 2 pathologists and assessed the relationship between Hp density and UBT values. The special stains evaluated for this study had similar accuracy based on estimated measures. Because IHC has a much higher cost than the other stains assessed here, either Warthin-Starry or Giemsa would be more cost-effective than IHC for improving Hp detection during the pathological assessment of stomach tissue biopsies relative to not using a special stain. The Hp density grades of the 2 pathologists showed good consistency of agreement. The Hp density grades were positively associated with UBT values. Considering the high global mortality from stomach cancer, a 2014 International Agency for Research on Cancer Hp Working Group recommended that countries explore the possibility of introducing Hp screening and treatment programs; this panel cautioned, however, that decisions about whether and how to implement such programs must be based on local considerations of disease burden and other factors of relevance to health policy. Identifying local indicators of high risk for targeted interventions is key for effective cancer prevention programs. Thus, understanding the relationship between Hp density and gastritis severity in specific populations at elevated risk of stomach cancer has great public health significance. In this thesis, I also investigated whether the frequency of severe Hp-associated gastritis increases as Hp density increases. To do this, I estimated the effect of Hp density on gastritis severity among Hp-positive participants in CANHelp community projects. This analysis used data from participants with stomach tissue biopsies collected from 2008 through 2017 in 7 CANHelp community projects. The results showed that gastritis severity increases sharply with increasing Hp density among Hp-positive participants.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,042 | 0,094 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,001 |
| Méta-épidémiologie (sens large) | 0,001 | 0,002 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,002 | 0,002 |
| Communication savante | 0,002 | 0,001 |
| Science ouverte | 0,001 | 0,002 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».