Urinary Podocalyxin May Flag Early Diabetic Nephropathy

Key Takeaways

• Among adults with T2DM studied in Dhaka, Bangladesh, urinary podocalyxin rose significantly across normoalbuminuric, microalbuminuric, and macroalbuminuric groups.
• At the main diabetic nephropathy cutoff, urinary podocalyxin classified albuminuric disease with 86.7% sensitivity and 100% specificity.
• Separate ROC analyses suggested distinct urinary podocalyxin thresholds across healthy-to-diabetes and successive albuminuria stage transitions.
• Higher u-PDX tracked greater albuminuria burden and lower kidney function.

Diabetic nephropathy can remain clinically silent while podocyte injury is already underway, so albumin-based testing may miss earlier glomerular damage. Urinary podocalyxin, a podocyte-shed glycoprotein measurable in spot urine, is being evaluated as a noninvasive marker of that injury in adults with type 2 diabetes mellitus (T2DM). In Dhaka, Bangladesh, investigators examined whether it could separate albuminuria stages within T2DM and distinguish albuminuric kidney involvement from nonalbuminuric disease.

In the Hossain et al. study of urinary podocalyxin in adults with type 2 diabetes, investigators conducted a cross-sectional analytical study at Bangabandhu Sheikh Mujib Medical University in Dhaka, Bangladesh, with recruitment from 25 March 2023 to 3 August 2024. The cohort included 88 adults: 59 with T2DM and 29 healthy controls, while the diabetes subgroup comprised 29 normoalbuminuric, 15 microalbuminuric, and 15 macroalbuminuric participants classified by urine albumin-to-creatinine ratio (uACR). Urinary podocalyxin (u-PDX) was measured in spot urine by enzyme-linked immunosorbent assay (ELISA) in duplicate, with intra-assay and inter-assay coefficients of variation below 8%, and the analysis included receiver operating characteristic (ROC) curves with bootstrap optimism correction plus adjusted Firth penalized logistic regression.

Among participants with T2DM, mean u-PDX rose from 1.16 ± 0.39 ng/mL in normoalbuminuria to 7.28 ± 2.05 ng/mL in macroalbuminuria across worsening albuminuria. The albuminuric diabetes group had nearly five-fold higher u-PDX than the nonalbuminuric group. u-PDX correlated most strongly with uACR (r = 0.79, p < 0.001) and inversely with estimated glomerular filtration rate (eGFR) (r = -0.51, p < 0.001).

For albuminuria-defined diabetic nephropathy within T2DM, urinary podocalyxin diagnostic performance in diabetic nephropathy showed an AUC of 0.96 (95% CI 0.90-1.00) at a 2.92 ng/mL cutoff, with 86.7% sensitivity and 100% specificity. Separate ROC analyses suggested different thresholds across transitions from healthy controls to normoalbuminuric diabetes and from earlier to more advanced albuminuria, and bootstrap correction showed little optimism.

Because the analysis was cross-sectional, single-center, and modest in size, it does not establish causality or prognostic value. Diabetic nephropathy was defined by uACR thresholds inside the same cohort, so uACR served as an internal classification reference rather than an independent comparator, and the ROC-derived cutoffs were generated and tested in the same dataset despite bootstrap correction. Participants taking renin-angiotensin system (RAS) inhibitors were excluded, which narrows direct applicability to routinely treated diabetic nephropathy populations.

The authors concluded that u-PDX tracked albuminuria severity and showed strong cross-sectional discrimination for diabetic nephropathy in adults with T2DM, but longitudinal and external validation are still needed before routine screening use.

Clinician Questions

How was diabetic nephropathy defined in the urinary podocalyxin analysis?

Among adults with T2DM, normoalbuminuria by uACR of less than 30 mg/g was treated as non-nephropathy, while microalbuminuria at 30-300 mg/g and macroalbuminuria above 300 mg/g were grouped as diabetic nephropathy; for that reason, uACR functioned as an internal classification reference rather than an independent diagnostic comparator.

What urinary podocalyxin thresholds separated healthy controls and successive albumuria stages in type 2 diabetes?

Pairwise ROC analyses in adults with T2DM reported a u-PDX threshold of 0.80 ng/mL for healthy controls versus normoalbuminuric T2DM with 100% sensitivity and 96.4% specificity, 1.60 ng/mL for normoalbuminuric versus microalbuminuric T2DM with 86.7% sensitivity and 93.1% specificity, and 5.51 ng/mL for microalbuminuric versus macroalbuminuric T2DM with 86.7% sensitivity and 93.3% specificity; bootstrap internal validation showed little optimism.

What classification performance accompanied the 2.92 ng/mL urinary podocalyxin cutoff for albuminuria-defined diabetic nephropathy?

In adults with T2DM, the 2.92 ng/mL u-PDX cutoff for albuminuria-defined diabetic nephropathy was accompanied by 100% positive predictive value, 89.9% negative predictive value, and 93.2% accuracy.

Did urinary podocalyxin remain associated with diabetic nephropathy after adjustment?

In adjusted Firth penalized logistic regression controlling for age, sex, duration of diabetes, and systolic blood pressure, each 1 ng/mL increase in u-PDX was associated with diabetic nephropathy (aOR 22.67, 95% CI 2.47-208.09; p = 0.006); the wide confidence interval and cross-sectional single-center design keep that finding exploratory.