Effects of Empagliflozin on Fluid Overload, Weight, and Blood Pressure in CKD

SIGNIFICANCE STATEMENT

SGLT2 inhibitors reduce risk of kidney progression, AKI, and cardiovascular disease, but the mechanisms of benefit are incompletely understood. Bioimpedance spectroscopy can estimate body water and fat mass. One quarter of the EMPA-KIDNEY bioimpedance substudy CKD population had clinically significant levels of bioimpedance-derived "Fluid Overload" at recruitment. Empagliflozin induced a prompt and sustained reduction in "Fluid Overload," irrespective of sex, diabetes, and baseline N-terminal pro B-type natriuretic peptide or eGFR. No significant effect on bioimpedance-derived fat mass was observed. The effects of SGLT2 inhibitors on body water may be one of the contributing mechanisms by which they mediate effects on cardiovascular risk.

BACKGROUND

CKD is associated with fluid excess that can be estimated by bioimpedance spectroscopy. We aimed to assess effects of sodium glucose co-transporter 2 inhibition on bioimpedance-derived "Fluid Overload" and adiposity in a CKD population.

METHODS

EMPA-KIDNEY was a double-blind placebo-controlled trial of empagliflozin 10 mg once daily in patients with CKD at risk of progression. In a substudy, bioimpedance measurements were added to the main trial procedures at randomization and at 2- and 18-month follow-up visits. The substudy's primary outcome was the study-average difference in absolute "Fluid Overload" (an estimate of excess extracellular water) analyzed using a mixed model repeated measures approach.

RESULTS

The 660 substudy participants were broadly representative of the 6609-participant trial population. Substudy mean baseline absolute "Fluid Overload" was 0.4±1.7 L. Compared with placebo, the overall mean absolute "Fluid Overload" difference among those allocated empagliflozin was -0.24 L (95% confidence interval [CI], -0.38 to -0.11), with similar sized differences at 2 and 18 months, and in prespecified subgroups. Total body water differences comprised between-group differences in extracellular water of -0.49 L (95% CI, -0.69 to -0.30, including the -0.24 L "Fluid Overload" difference) and a -0.30 L (95% CI, -0.57 to -0.03) difference in intracellular water. There was no significant effect of empagliflozin on bioimpedance-derived adipose tissue mass (-0.28 kg [95% CI, -1.41 to 0.85]). The between-group difference in weight was -0.7 kg (95% CI, -1.3 to -0.1).

CONCLUSIONS

In a broad range of patients with CKD, empagliflozin resulted in a sustained reduction in a bioimpedance-derived estimate of fluid overload, with no statistically significant effect on fat mass.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT03594110 ; EuDRACT: 2017-002971-24 ( https://eudract.ema.europa.eu/ ).

Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Determining the Relationship Between Blood Pressure, Kidney Function, and Chronic Kidney Disease: Insights From Genetic Epidemiology

BACKGROUND

It is well established that decreased kidney function can increase blood pressure (BP), but it is unproven whether moderately elevated BP causes chronic kidney disease (CKD) or glomerular hyperfiltration.

METHODS

311 119 White British UK Biobank participants were included in logistic regression analyses to estimate the odds of CKD (defined as long-term kidney replacement therapy, estimated glomerular filtration rate [eGFR]< 60mL/min/1.73m², or urinary albumin:creatinine ratio ≥3 mg/mmol) associated with higher genetically predicted BP using genetic risk scores comprising 219 systolic and 223 diastolic BP loci. Analyses estimating associations with clinical categories of eGFR and urinary albumin:creatinine ratio were also conducted, with an eGFR ≥120 mL (min·1.73m²) considered evidence of glomerular hyperfiltration.

RESULTS

21 623 participants had CKD: 7781 with reduced eGFR and 15 500 with albuminuria. 1828 participants had an eGFR ≥120 mL/min/1.73m². Each genetically predicted 10 mmHg higher systolic BP and 5 mmHg higher diastolic BP were associated with a 37% (95% CI, 1.29-1.45) and 19% (1.14-1.25) higher odds of CKD, respectively. Associations were evident for both the reduced eGFR and albuminuria components of the CKD outcome. The odds of hyperfiltration (versus an eGFR ≥60 and <90 mL/min/1.73m² were 49% higher (95% CI, 1.21-1.84) for each genetically predicted 10 mmHg higher systolic BP. Associations with CKD and hyperfiltration were similar irrespective of preexisting diabetes, vascular disease, or different levels of adiposity.

CONCLUSIONS

In this general population, genetic epidemiological evidence supports a causal role of life-long differences in BP for decreased kidney function, glomerular hyperfiltration, and albuminuria. Physiological autoregulation may not afford complete renal protection against the moderate BP elevations.

TaleNeprilysin and Neprilysin inhibition in chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is associated with increased risk of progression to end-stage kidney disease and cardiovascular events. There is limited evidence that available treatments have beneficial effects on cardiorenal outcomes in all people with nondiabetic CKD. Neprilysin inhibition (NEPi) is a new therapeutic strategy with potential to improve outcomes for patients with CKD.

RECENT FINDINGS

NEPi enhances the activity of the natriuretic peptide system producing natriuresis, diuresis and inhibition of the renin-angiotensin system and sympathetic nervous system. Sacubitril/valsartan is the first Angiotensin receptor-neprilysin inhibitor (ARNI) to be produced and has been shown to substantially improve cardiovascular outcomes in heart failure and delay progression of kidney disease in this population. Although ARNIs have not shown similar effects on kidney function in the short-to-medium term in people with CKD, they are associated with substantial reductions in cardiac biomarkers and blood pressure in CKD.

SUMMARY

These data suggest that NEPi with an ARNI could benefit patients with CKD by reducing the risk of cardiovascular disease and have the possibility of retarding the progression of CKD (hence delaying the need for renal replacement therapy).

Chronic kidney disease, heart failure and neprilysin inhibition

Patients with chronic kidney disease are at increased risk of cardiovascular disease and this often manifests clinically like heart failure. Conversely, patients with heart failure frequently have reduced kidney function. The links between the kidneys and cardiovascular system are being elucidated, with blood pressure being a key risk factor. Patients with heart failure have benefitted from many trials which have now established a strong evidence based on which to base management. However, patients with advanced kidney disease have often been excluded from these trials. Nevertheless, there is little evidence that the benefits of such treatments are modified by the presence or absence of kidney disease, but more direct evidence among patients with advanced kidney disease is required. Neprilysin inhibition is the most recent treatment to be shown to improve outcomes among patients with heart failure. The UK HARP-III trial assessed whether neprilysin inhibition improved kidney function in the short- to medium-term and its effects on cardiovascular biomarkers. Although no effect (compared to irbesartan control) was found on kidney function, allocation to neprilysin inhibition (sacubitril/valsartan) did reduce cardiac biomarkers more than irbesartan, suggesting that this treatment might improve cardiovascular outcomes in this population. Larger clinical outcomes trials are needed to test this hypothesis.

Effects of Sacubitril/Valsartan Versus Irbesartan in Patients With Chronic Kidney Disease

BACKGROUND

Sacubitril/valsartan reduces the risk of cardiovascular mortality among patients with heart failure with reduced ejection fraction, but its effects on kidney function and cardiac biomarkers in people with moderate to severe chronic kidney disease are unknown.

METHODS

The UK HARP-III trial (United Kingdom Heart and Renal Protection-III), a randomized double-blind trial, included 414 participants with an estimated glomerular filtration rate (GFR) 20 to 60 mL/min/1.73 m² who were randomly assigned to sacubitril/valsartan 97/103 mg twice daily versus irbesartan 300 mg once daily. The primary outcome was measured GFR at 12 months using ANCOVA with adjustment for each individual's baseline measured GFR. All analyses were by intention to treat.

RESULTS

In total, 207 participants were assigned to sacubitril/valsartan and 207 to irbesartan. Baseline measured GFR was 34.0 (SE, 0.8) and 34.7 (SE, 0.8) mL/min/1.73 m², respectively. At 12 months, there was no difference in measured GFR: 29.8 (SE 0.5) among those assigned sacubitril/valsartan versus 29.9 (SE, 0.5) mL/min/1.73 m² among those assigned irbesartan; difference, -0.1 (0.7) mL/min/1.73 m². Effects were similar in all prespecified subgroups. There was also no significant difference in estimated GFR at 3, 6, 9, or 12 months and no clear difference in urinary albumin:creatinine ratio between treatment arms (study average difference, -9%; 95% CI, -18 to 1). However, compared with irbesartan, allocation to sacubitril/valsartan reduced study average systolic and diastolic blood pressure by 5.4 (95% CI, 3.4-7.4) and 2.1 (95% CI, 1.0-3.3) mm Hg and levels of troponin I and N terminal of prohormone brain natriuretic peptide (tertiary end points) by 16% (95% CI, 8-23) and 18% (95% CI, 11-25), respectively. The incidence of serious adverse events (29.5% versus 28.5%; rate ratio, 1.07; 95% CI, 0.75-1.53), nonserious adverse reactions (36.7% versus 28.0%; rate ratio, 1.35; 95% CI, 0.96-1.90), and potassium ≥5.5 mmol/L (32% versus 24%, P=0.10) was not significantly different between randomized groups.

CONCLUSIONS

Over 12 months, sacubitril/valsartan has similar effects on kidney function and albuminuria to irbesartan, but it has the additional effect of lowering blood pressure and cardiac biomarkers in people with chronic kidney disease.

CLINICAL TRIAL REGISTRATION

URL: http://www.isrctn.com . Unique identifier: ISRCTN11958993.

Campath, calcineurin inhibitor reduction, and chronic allograft nephropathy (the 3C Study) - results of a randomized controlled clinical trial

Calcineurin inhibitors (CNIs, eg, tacrolimus) reduce short-term kidney transplant failure, but chronic nephrotoxicity may contribute to late transplant loss. Elective conversion to inhibitors of the mammalian target of rapamycin (mTOR, eg, sirolimus) pathway might avoid long-term CNI renal damage and improve outcomes. The 3C Study was a pragmatic randomized controlled trial of sequential randomizations between alemtuzumab and basiliximab induction therapy (at the time of surgery) and between tacrolimus and sirolimus maintenance therapy at 6 months posttransplantation. The primary outcome of this analysis was estimated glomerular filtration rate (eGFR) at 18 months after maintenance therapy randomization; 197 patients were assigned sirolimus-based and 197 to tacrolimus-based therapy. Allocation to sirolimus had no significant effect on eGFR at 18 months: baseline-adjusted mean (SEM) eGFR was 53.7 (0.9) mL/min/1.73 m² in the sirolimus group versus 54.6 (0.9) mL/min/1.73 m² in the tacrolimus group (P = .50). Biopsy-proven acute rejection (29 [14.7%]) vs 6 [3.0%]; P < .001) and serious infections (defined as opportunistic infections or those requiring hospitalization; 95 [48.2%] vs 70 [35.5%]; P = .008) were more common among participants allocated sirolimus. Compared with tacrolimus-based therapy, sirolimus-based maintenance therapy did not improve transplant function at 18 months after conversion and was associated with significant hazards of rejection and infection. ClinicalTrials.gov identifier NCT01120028 and ISRCTN88894088.

Biliary Tract and Liver Complications in Polycystic Kidney Disease

Polycystic liver disease is a well described manifestation of autosomal dominant polycystic kidney disease (ADPKD). Biliary tract complications are less well recognized. We report a 50-year single-center experience of 1007 patients, which raised a hypothesis that ADPKD is associated with biliary tract disease. We tested this hypothesis using all England Hospital Episode Statistics data (1998-2012), within which we identified 23,454 people with ADPKD and 6,412,754 hospital controls. Hospitalization rates for biliary tract disease, serious liver complications, and a range of other known ADPKD manifestations were adjusted for potential confounders. Compared with non-ADPKD hospital controls, those with ADPKD had higher rates of admission for biliary tract disease (rate ratio [RR], 2.24; 95% confidence interval [95% CI], 2.16 to 2.33) and serious liver complications (RR, 4.67; 95% CI, 4.35 to 5.02). In analyses restricted to those on maintenance dialysis or with a kidney transplant, RRs attenuated substantially, but ADPKD remained associated with biliary tract disease (RR, 1.19; 95% CI, 1.08 to 1.31) and perhaps with serious liver complications (RR, 1.15; 95% CI, 0.98 to 1.33). The ADPKD versus non-ADPKD RRs for biliary tract disease were larger for men than women (heterogeneity P<0.001), but RRs for serious liver complications appeared higher in women (heterogeneity P<0.001). Absolute excess risk of biliary tract disease associated with ADPKD was larger than that for serious liver disease, cerebral aneurysms, and inguinal hernias but less than that for urinary tract infections. Overall, biliary tract disease seems to be a distinct and important extrarenal complication of ADPKD.

Use of Causal Diagrams to Inform the Design and Interpretation of Observational Studies: An Example from the Study of Heart and Renal Protection (SHARP)

Observational studies often seek to estimate the causal relevance of an exposure to an outcome of interest. However, many possible biases can arise when estimating such relationships, in particular bias because of confounding. To control for confounding properly, careful consideration of the nature of the assumed relationships between the exposure, the outcome, and other characteristics is required. Causal diagrams provide a simple graphic means of displaying such relationships, describing the assumptions made, and allowing for the identification of a set of characteristics that should be taken into account (i.e., adjusted for) in any analysis. Furthermore, causal diagrams can be used to identify other possible sources of bias (such as selection bias), which if understood from the outset, can inform the planning of appropriate analyses. In this article, we review the basic theory of causal diagrams and describe some of the methods available to identify which characteristics need to be taken into account when estimating the total effect of an exposure on an outcome. In doing so, we review the concept of collider bias and show how it is inappropriate to adjust for characteristics that may be influenced, directly or indirectly, by both the exposure and the outcome of interest. A motivating example is taken from the Study of Heart and Renal Protection, in which the relevance of smoking to progression to ESRD is considered.

Evidence for Reverse Causality in the Association Between Blood Pressure and Cardiovascular Risk in Patients With Chronic Kidney Disease

Supplemental Digital Content is available in the text.

Among those with moderate-to-advanced chronic kidney disease, the relationship between blood pressure (BP) and cardiovascular disease seems U shaped but is loglinear in apparently healthy adults. The SHARP (Study of Heart and Renal Protection) randomized 9270 patients with chronic kidney disease to ezetimibe/simvastatin versus matching placebo and measured BP at each follow-up visit. Cox regression was used to assess the association between BP and risk of cardiovascular disease among (1) those with a self-reported history of cardiovascular disease and (2) those with no such history and, based on plasma troponin-I concentration, a low probability of subclinical cardiac disease. A total of 8666 participants had a valid baseline BP and troponin-I measurement, and 2188 had at least 1 cardiovascular event during follow-up. After adjustment for relevant confounders, the association between systolic BP and cardiovascular events was U shaped, but among participants without evidence of previous cardiovascular disease, there was a positive loglinear association throughout the range of values studied. Among those with the lowest probability of subclinical cardiac disease, each 10 mm Hg higher systolic BP corresponded to a 27% increased risk of cardiovascular disease (hazard ratio, 1.27; 95% confidence interval, 1.11–1.44). In contrast, the relationship between diastolic BP and cardiovascular risk remained U shaped irrespective of cardiovascular disease history or risk of subclinical disease. In conclusion, the lack of a clear association between systolic BP and cardiovascular risk in this population seems attributable to confounding, suggesting that more intensive systolic BP reduction may be beneficial in such patients.

Outcomes of Elderly Patients with Anti-Neutrophil Cytoplasmic Autoantibody-Associated Vasculitis Treated with Immunosuppressive Therapy

BACKGROUND/AIMS

Anti-neutrophil cytoplasmic autoantibody-associated vasculitis (AAV) is a cause of biopsy-proven acute kidney injury, more common in the elderly. Treatment requires immunosuppression, which can have significant toxic effects. The aim of this study was to assess whether morbidity and mortality that are associated with immunosuppression for AAV varied with age.

METHODS

A retrospective review of 232 patients given induction therapy with prednisolone and cyclophosphamide was conducted. Information was collected on baseline characteristics (including requirement for dialysis at presentation) and the occurrence of leukopenia, infection, end-stage renal disease and death during follow-up.

RESULTS

Median follow-up was 51 months. Older patients (aged ≥70 years) were treated with lower total cyclophosphamide doses than those aged <70 years (mean 7.3 g (SD 4.4) vs. 10.7 g (SD 7.4), respectively). Increasing age was associated with an increased risk of leukopenia (odds ratio (OR) 1.50; 95% confidence interval (CI) 1.20-1.86; p < 0.001), and older patients were more likely to develop infections in the first year (OR 1.87; 95% CI 1.1-3.2). Older patients were also significantly more likely to require dialysis at presentation (OR 1.66; 95% CI 1.13-2.5) and longer term. After multivariable adjustment, age and requirement for dialysis at presentation were significant predictors of death (hazard ratio (HR) per year of age 1.07; 95% CI 1.03-1.11; p < 0.001 and HR 2.2; 95% CI 1.10-4.38; p = 0.03, respectively).

CONCLUSIONS

Among patients treated with prednisolone and cyclophosphamide, increasing age and dialysis dependency were associated with worse survival. Older patients were more likely to develop treatment-related complications despite lower cumulative doses of immunosuppression. Morbidity and mortality associated with treatment must therefore be carefully balanced against that associated with the disease process itself.

Cross-sectional and longitudinal association of the secretoglobin 1A1 gene A38G polymorphism with asthma phenotype in the Perth Infant Asthma Follow-up cohort

BACKGROUND

Associations between Clara cell secretory protein gene variants (SCGB1A1, also known as CC16, CC10, CCSP and uteroglobin) and the asthma phenotype have been found in five out of eight studies world-wide. No study has investigated the contribution of SCGB1A1 polymorphisms to the development and/or persistence of the asthma phenotype in a birth cohort followed over time.

OBJECTIVE

The aim of this study was to determine the role of the SCGB1A1 gene in the development of the asthma phenotype.

METHODS

The Perth Infant Asthma Follow-up (PIAF) cohort (n=231 unrelated infants, unselected for asthma and recruited at birth) were seen at 1 month, 6 and 11 years of age, and had a questionnaire, lung function, airway responsiveness (AR) and skin prick tests (SPTs) completed. Blood was taken at 6 and 11 years for total and specific immunoglobulin E (sIgE) and DNA extraction. SPT positivity had at least one positive SPT. SIgE>4 kU/L had at least one sIgE above 4 kU/L. SCGB1A1 A38G (rs3741240), that alters gene transcription, was genotyped using Sau96I restriction digestion of exon 1 PCR products.

RESULTS

At 6 and 11 years of age, 33.0% and 29.7% of those genotyped had doctor-diagnosed asthma, and 35.8% and 52.1% had SPT positivity. In cross-sectional analyses, children with 38G/38A or 38A/38A had increased AR at 1 month (1.72-fold, P=0.013); sIgE>4 kU/L [odds ratio (OR)=6.95, 95% confidence interval (CI)=1.35-35.91, P=0.021]; house dust mite (HDM) SPT positivity (OR=7.21, 95% CI=1.09-47.78, P=0.041) and sIgE (4.57-fold, P=0.045) at 6 years; and doctor-diagnosed asthma (OR=3.93, 95% CI=1.24-12.47, P=0.02) and cat SPT positivity (OR=4.34, 95% CI=1.01-18.77, P=0.049) at 11 years. Longitudinal analyses of 6 and 11 years paired data showed that children with 38A/38A had increased persistent sIgE>4 kU/L (OR=11.87, 95% CI=1.97-71.53, P=0.007) and persistent HDM SPT positivity (OR=7.84, 95% CI=1.04-58.92, P=0.045).

CONCLUSION

SCGB1A1 A38G may play a role in the development and persistence of the asthma phenotype in childhood.