Data quality and patient characteristics in European ANCA-associated vasculitis registries: data retrieval by federated querying

OBJECTIVES

This study aims to describe the data structure and harmonisation process, explore data quality and define characteristics, treatment, and outcomes of patients across six federated antineutrophil cytoplasmic antibody-associated vasculitis (AAV) registries.

METHODS

Through creation of the vasculitis-specific Findable, Accessible, Interoperable, Reusable, VASCulitis ontology, we harmonised the registries and enabled semantic interoperability. We assessed data quality across the domains of uniqueness, consistency, completeness and correctness. Aggregated data were retrieved using the semantic query language SPARQL Protocol and Resource Description Framework Query Language (SPARQL) and outcome rates were assessed through random effects meta-analysis.

RESULTS

A total of 5282 cases of AAV were identified. Uniqueness and data-type consistency were 100% across all assessed variables. Completeness and correctness varied from 49%-100% to 60%-100%, respectively. There were 2754 (52.1%) cases classified as granulomatosis with polyangiitis (GPA), 1580 (29.9%) as microscopic polyangiitis and 937 (17.7%) as eosinophilic GPA. The pattern of organ involvement included: lung in 3281 (65.1%), ear-nose-throat in 2860 (56.7%) and kidney in 2534 (50.2%). Intravenous cyclophosphamide was used as remission induction therapy in 982 (50.7%), rituximab in 505 (17.7%) and pulsed intravenous glucocorticoid use was highly variable (11%-91%). Overall mortality and incidence rates of end-stage kidney disease were 28.8 (95% CI 19.7 to 42.2) and 24.8 (95% CI 19.7 to 31.1) per 1000 patient-years, respectively.

CONCLUSIONS

In the largest reported AAV cohort-study, we federated patient registries using semantic web technologies and highlighted concerns about data quality. The comparison of patient characteristics, treatment and outcomes was hampered by heterogeneous recruitment settings.

Blood-platelets-damaging activity of some synthetic Streptococcus peptidoglycan subunits and analogues

A series of 25 synthetic subunits or analogues of streptococcal peptidoglycan was tested for their ability to damage rabbit blood platelets. The morphological changes of the platelets were studied on an ultrastructural level. Minimal subunit structure able to produce a complete lysis of the platelets was found to be muramyldipeptide (MDP). Comparable lysis of platelets was also caused by muramyltetrapeptide and MDP containing D-Ala instead of L-Ala. The lytic effect was dose-dependent and was exhibited rather after high doses of the substances used (up to 500 micrograms/ml). For the lytic reaction, the configuration of C3 and C4 in the muramyl residue of MDP was essential. Many substances produced only degranulation without lysis of the platelets and some of them did not influence the platelet ultrastructure at all. The paper presents some structure-to-function relationships of the compounds and shows that the platelet-damaging activity of peptidoglycan may be related to certain portions of the peptidoglycan molecule. This activity should be tested when the immunomodulatory substances derived from the bacterial peptidoglycan are searched for.

Biological Activity of Synthetic Subunits of Streptococcus Peptidoglycan

Each of a series of synthetic peptidoglycan subunits and subunit analogues was injected in combination with streptococcus type M24 antigen extract. The substances tested were: (8a) N-acetylmuramyldipeptide (MDP) and the following derivatives thereof: MDP modified in positions C3 and C4, or with <i>L</i>-alanine substituted by <i>L</i>-2-aminobutyric acid or with the peptidic chain prolonged (by three lysines or a polylysine); (b) some synthetically prepared peptides: a hexapeptide, a tridecapeptide and an octadecapeptide. Configurations in positions C3 and C4 were found essential for the adjuvant effect. Adjuvant activity, though somewhat lower than in MDP, was pronounced in the analogue containing the <i>L</i>-2-aminobutyryl residue. Surprisingly, potent adjuvant effect was displayed by the hexapeptide; prolongation of the peptidic chain was not effective. The use of a polymeric carrier for MDP increased the adjuvant effect. Contrary to expectation, streptococcal antigens used with immunoadjuvant materials showed that induced delayed hypersensitivity was type related.

Biological Activity of Synthetic Subunits of Streptococcus Peptidoglycan

A series of synthetic subunits and analogues of streptococcal peptidoglycan was prepared and used in fever and tolerance experiments on rabbits. The lengthening of the chain of the peptide moiety of peptidoglycan did not result in pyrogenic activity, except for hexa-peptide. Attachment of the muramyl residue rendered the peptides pyrogenic. The activity of such materials varied in degree and was rather in an indirect relation to peptide chain length. A change in the configuration of C4-OH or C3-OR in the muramyl residue resulted in a profound decrease in pyrogenicity. No inhibitory effect of N-acetylmuramyl-.<i>D</i>-alanyl- <i>D</i>-iso-glutamine on muramyldipeptide (MDP) pyrogenicity could be demonstrated. Repeated administration of MDP resulted in the induction of tolerance to the pyrogenicity of this substance in rabbits. These animals were not tolerant to the pyrogenicity of peptidoglycan. Nontolerance was also observed in reciprocal experiments with these materials as well as in trials with hexapeptide and peptidoglycan given in either order. The data are consistent with the assumption that peptidoglycan contains more than one biologically active subunit. There is a structure-to-function relationship. The knowledge of the biological effects of the synthetic analogues is essential for the prospect of their use under model or human conditions.