In the NEWS: New biomarkers for AIN

Acute interstitial nephritis (AIN) is the cause of over 15% cases of acute loss of kidney function Unlike many other causes of acute loss of kidney function, AIN is treatable with steroids if culprit is stopped in many occasions. Diagnosis of AIN is often difficult and there have been various markers in the history of AIN

Currently, AIN commonly occurs because of various non–β-lactam antibiotics, proton pump inhibitors, nonsteroidal antiinflammatory drugs, and cancer immunotherapy agents.

The classical triad of rash, fever and AKI doesn’t always exist in all cases. In addition, while seen many times, not all cases have a peripheral eosinophilia. A trend of rising eosinophils is often noted in several cases. 

The classically used urine eosinophils was thrown under the bus few years ago. Yet, many still order that test that is very non specific and not sensitive for AIN.

Imaging studies such as MAG-3 scans are rarely used and not as sensitive or specific for AIN. A kidney biopsy is often needed before giving steroids. Often this is not possible due to active infection, recent infection, anticoagulation.

A recent study published in JCI shows some novel urinary markers that might be used to diagnosis AIN. In a single center, 15% of patients had AIN. Participants with AIN had consistently higher levels of urine TNF-α and IL-9 than those with other diagnoses, including acute tubular injury, glomerular diseases, and diabetic kidney disease, and those without any kidney disease. The higher the TNF and IL-9, the higher the index of renal biopsy injury. The kidney biopsies with AIN also stained highly with TNF and IL-9.  In addition, the clinicians diagnosis index improved significantly with addition of these urinary markers.

AIN is a tough diagnosis to make. This study adds value in perhaps using other biomarkers that show signs of T cell activation. Is this specific for renal disease is a trend to watch? To me, there are no clinical signs that are real obvious clues. Urine eos- most useless, MAG-3 scans,- not useful. Serum eos trends- maybe useful. Urine WBCS casts and WBCS- not specific. The current study adds to the most specific findings thus far for an AIN diagnosis

Consult Rounds: Heavy Chain Deposition Disease

Heavy-chain deposition disease (HCDD) is the least common non-organized monoclonal immunoglobulin deposition disease (MIDD), with close to 50 documented cases in world literature to date. The existence of this entity was postulated for many years until the first case was reported by Tubbs et al. in 1982 followed by another report by Aucouturier et al. in 1993.

It is mostly characterized by γ-heavy chain(HC), and occasionally α-HC, μ--HC,  or δ-HC deposits. Nearly half of HCDD cases were in patients without a symptomatic B-cell disorder, a condition now referred to as monoclonal gammopathy  of renal significance (MGRS).  A constant biochemical characteristic of deposited HC is the deletion of the first constant domain (CH1), which is required for the secretion of an isolated free HC. Other pathologic and clinical features differ from those of LCDD, including the higher frequency of nodular glomerulosclerosis, hypertension, hematuria, and serum hypocomplementemia in g-HCDD.

Recent studies have confirmed that the heavy chain with complement components, mostly C3 and C1q, is frequent in γ 3- and γ 1-HCDD with hypocomplementemia. These findings have been attributed to the capacity of IgG3 and, to a lesser extent, IgG1, to activate the complement classic pathway through C1q binding to the CH2 domain. Whether local and/or systemic complement classic pathway activation is involved in the pathogenesis of γ -HCDD remains unclear.

So what really happens?

When there is the CH1 domain lacking in the heavy chain, this doesn’t allow for the heavy chain binding to it’s chaperone protein in the endoplasmic reticulum, resulting in a truncated heavy chain by the B cell or plasma cell clone. This then starts depositing as it has a higher affinity to tissue- mainly the kidney! Even a small amount of it can cause damage. Hence, most of these cases didn’t have full blown myeloma but bone marrow showed in most as MGUS or smoldering myeloma.  Interestingly, in this latest study by Bridoux et al in 2017, they showed that in over 60% of the cases they reported, there was an abnormal serum free light chain ratio and a positive free light chain immunofixation as well. Interestingly, free light-chain assay levels correlated with disease response in the majority of patients. This suggests that the underlying B- or plasma cell clone produces a monoclonal light chain in addition to the pathogenic heavy chain, and thus the serum-free light-chain assay can be useful in HCDD diagnosis and monitoring after treatment.

Earlier studies had shown that there is a grim prognosis for HCDD. I think this might have been before MGRS was defined and many of them never got treated with anti-plasma cell agents. In the post bortezomib era, the newer data suggests otherwise. Bridoux et al from France data suggests that the outcomes were not that grim and the response to proteasome inhibitors were excellent. Recent mouse models have shown that this efficient response to proteasome inhibitors mostly relies on the presence of the isolated truncated heavy chain that sensitizes plasma cells to bortezomib through an elevated unfolded protein response.

So in summary

HCDD is rare but is a form of MIDD

Most commonly associated with MGUS or smoldering myeloma

The most common HC involved is γ and IgG3 specific

It is not unusual to see hypocomplementemia with this entity

Nodular sclerosis is the pathology finding on light microscopy

Response to proteasome inhibitors appears promising

Topic Discussion: Newer Gadolinium agents and risk of NSF? is it extinct?

Gadolinium is known to have an association with Nephrogenic Systemic Fibrosis(NSF). The first case of this was described in Yale and published in Lancet. A potential link between NSF and the application of gadolinium-based contrast agents (GBCAs) was first described by Grobner et al in 2006. The risk of gadolinium based contrast agents to trigger NSF seems to be related to the stability of the agent. Thus, nonionic linear gadolinium based contrast agents are more likely to trigger NSF than ionic linear agents both of which are distinctly more likely to trigger the disease than the macrocyclic agents in patients with reduced renal function. Gadobutrol (Gadovist, Gadavist) is a second-generation nonionic, multipurpose, extracellular, macrocyclic gadolinium based contrast agent provided in a 1 molar concentration. As a macrocyclic contrast agent, gadobutrol provides high chelate stability with substantially less—if any—in vivo release of Gd ions as opposed to linear gadolinium (old school agents). The release of gadolinium ions has been linked to an increased risk of NSF in patients with impaired renal function. The highest prevalence of NSF was associated with Omniscan, Optimark as most of these have a weak binding of gadolinium to the chelate. 

So are these safer? A large study published in 2017 was a prospective, international, multicenter, open-label study in 55 centers. Patients with moderate to severe renal impairment scheduled for any gadobutrol-enhanced MRI were included. All patients received a single intravenous bolus injection of gadobutrol at a dose of 0.1 mmol/kg body weight. The primary target variable was the number of patients who develop NSF within a 2-year follow-up period. A total of 908 patients were enrolled, including 586 with moderate and 284 with severe renal impairment who are at highest risk for developing NSF. Overall, 184 patients (20.3%) underwent further contrast-enhanced MRI with other gadolinium-based contrast agents within the 2-year follow-up. No patient developed symptoms conclusive of NSF.

Another study by Lauenstein et al, investigated gadoxetate disodium in 357 patients. No case of NSF was recorded. Another recent study by Amet et al investigated the risk of gadoteric acid in 255 patients on dialysis with no findings of NSF. In addition, Soulez et al reported 2 prospective 2-year studies in 534 patients with either stage 3 chronic kidney disease (CKD) or stage 4 to 5 CKD. No signs or symptoms of NSF were reported after administration of gadobenate dimeglumine or gadoteridol. Smorodinsky et al retrospectively evaluated 1167 patients with chronic liver disease where 72% also had some degree of renal insufficiency. They did not report any case of NSF.

A recent Canadian society published their analysis and concluded that “In patients with AKI and category G4 and G5 CKD (eGFR < 30 mL/min/1.73 m²) and in dialysis-dependent patients who require Gadolinium based contrast agentss-enhanced MRI, they can be administered with exceedingly low risk of causing NSF when using macrocyclic agents and newer linear agents at routine doses.”

Here are images online from medscape education that are very useful on this matter.

A lot of centers in the world are now carrying and using Gadovist and perhaps we won’t see any NSF? 

In the NEWS: Credence, Rise of the Nephron Throne

A positive light at the end of the tunnel for nephrology, the Credence trial just got published this week in NEJM, put the glucoretics on top for diabetic nephropathy. When you search “credence” in the oxford dictionary it means” belief in or acceptance of something as true”.  I think the time has come to believe that SGLT-2 inhibitors are here to stay and are going to change the disease of diabetic nephropathy.

In summary, this large RCT was stopped early. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m²), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group. The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34%  and the relative risk of end-stage kidney disease was lower by 32%. The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke and hospitalization for heart failure. There were no significant differences in rates of amputation or fracture.

Some of the twitter world made some amazing comments on this

Susan Quaggin‏ @SusanQuaggin" 19 years since RENAAL and IDNT..followed by a series of negative trials...but the drought is over! New therapies for our patients with diabetic kidney disease are a reality - #CREDENCE marks the beginning of a new era in Kidney Medicine "#SockItToKidneyDisease"

Juan Manuel Mejía‏ @Meyaix "Every nephrologist is now talking of #CREDENCE ."

Jennie Lin, MD MTR‏ @jenniejlin"#CREDENCE, landmark clinical trial for patients with T2DM and kidney disease, is now published: 30% lower relative risk for primary renal outcome in canagliflozin arm, with pretty darn significant p-value of 0.00001! It was thrilling to watch the results stream live from #ISNWCN!"

And my personal favorite....

Steven Coca‏ @scoca1 "You had me at “hello” before the gasp & applause for the tiny p value The separation of the KM curves (effect size) and 95% CI are what had me leaping And more fist pumping when the difference in eGFR slopes were shown"

While this drug was developed and marketed to treat diabetes, it is more than that. Someone on social media world rightly said” We have an anti HTN and renal protective med that has a nice side effect of lowering your A1c”

It decreases blood pressure

It induces weight loss

It decreases intraglomerular pressure

It is a proximal tubular diuretic

It is anti-inflammation

It decreases proteinuria

This is a nephrologist's drug! Finally, we have a positive trial in the making that is going to change the practice of nephrology. Diabetics, non-diabetics, HTN, CHF patients- all might benefit from this discovery!

 

Topic Discussion: Hereditary transthyretin amyloidosis, inotersen and the kidney

Hereditary transthyretin amyloidosis is caused by pathogenic single-nucleotide variants in the gene encoding transthyretin (TTR) that induce transthyretin misfolding and systemic deposition of amyloid. Progressive amyloid accumulation leads to multiorgan dysfunction and death. Renal involvement is not as common as CNS and or cardiac involvement. A review in CJASN in 2012 had commented on the renal manifestations of this entity. Renal presentation usually is chronic kidney disease, proteinuria and kidney biopsy showing amyloid deposition.

Recently, novel therapies have emerged in the treatment of this entity in the neurology and the cardiology literature. Inotersen, a 2′-O-methoxyethyl–modified antisense oligonucleotide, inhibits hepatic production of transthyretin.  This study was published in NEJM last year and it was a randomized, double-blind, placebo-controlled, 15-month, phase 3 trial of inotersen in adults with stage 1 (patient is ambulatory) or stage 2 (patient is ambulatory with assistance) hereditary transthyretin amyloidosis with polyneuropathy. Inotersen improved the course of neurologic disease and quality of life in patients with hereditary transthyretin amyloidosis. What was interesting was that the most frequent serious adverse events in the inotersen group were glomerulonephritis(GN) (in 3 patients [3%]) and thrombocytopenia (in 3 patients [3%]), with one death associated with one of the cases of grade 4 thrombocytopenia. Apparently, it’s a black box warning now with this agent that is given SQ.

In reviewing the NEJM paper, they discuss that each of these three patients that developed the GN carried the Val30Met TTR mutation (148G→A) mutation. Two had shown a decline in the eGFR. In all three cases, the kidney biopsy showed complex pathologic features, consistent with crescentic glomerulonephritis superimposed on a background of amyloidosis and (in two cases) interstitial fibrosis. One patient was successfully treated with glucocorticoids and cyclophosphamide and regained clinically significant renal function. Another patient did not receive immunosuppressive therapy owing to delayed diagnosis, and permanent hemodialysis was initiated. A third patient was identified as having clinically significant proteinuria after the implementation of more frequent renal monitoring of every 2 to 3 weeks; this patient did not show a decline in renal function. Urinary protein excretion returned to baseline levels after treatment with glucocorticoids. There is no discussion on the serologies sent or if this was a vasculitic reaction that we see sometimes with anti TNF agents. After the notice of the GN in these patients, they instituted an enhanced monitoring system. After the implementation of enhanced monitoring, no additional cases of severe thrombocytopenia occurred, and a single case of glomerulonephritis was identified early without loss of renal function. There was also a single case of antineutrophil cytoplasmic autoantibody (ANCA)–positive systemic vasculitis reported. It is possible(speculative) that this drug induces an ANCA associated crescentic GN in certain cases. On a pubmed and google search, I found no further published cases of any GNs with this agent. Since the advent of this agent, several other agents are in the market for treatment of Transthyretin Amyloid neuropathy and cardiomyopathy.

A similar drug called Patisiran, an RNAi therapeutic for similar indication was published in 2018 as well. The investigators found that this drug significantly improved neuropathy in patients with hereditary transthyretin amyloidosis. This drug had no renal side effects reported in the side effect profile. This is an IV drug compared to the SQ version previously discussed. 

In another NEJM paper, in patients with transthyretin amyloid cardiomyopathy, tafamidis( oral transthyretin stabilizer)  was associated with reductions in all-cause mortality and cardiovascular-related hospitalizations and reduced the decline in functional capacity and quality of life as compared with placebo. The renal side effects were not significant in this drug and in equal frequency as the placebo arm.

So as the field of transthyretin amyloidosis is expanding, some of these novel targeted therapies can change the renal effects of this disease. As nephrologists, we need to be watchful for the glomerular side effects of inotersen.

Topic Discussion: Why does OncoNephrology matter?

Cancer affects the kidney in many ways. Education of the cancer specialists is important. Lately I have felt that the "kidney" has been ignored in many ways in the oncology world.

Recently, a review was published in NEJM on cancer survivorship and how long patients with cancer are living and the non cancer related complications. There was no mention of CKD and kidney related complications. Several studies have shown that CKD is an independent factor for mortality and cancer related mortality in cancer patients.  Few of us wrote a letter to the editor raising this concern. The response from the author was that “ CKD has a high mortality and not specific to cancer survivors”. This is an important message for our heme/onc colleagues to understand that CKD can add to the risk for cancer survivors. Having early nephrology care and co-managing and preparing for CKD related complications is important.

Another important ignored concept in Oncology is lack of studies that include patients with low GFR. In a recent analysis published in JAMA, Eighty-five percent of recent trials of therapies for the 5 most common malignancies (published in selected high–impact factor journals) excluded patients with CKD. This proportion exceeds that observed in cardiovascular trials published from 1985 through 2005. This finding is concerning because it was estimated that 32% of deaths among patients with CKD in 2005-2009 were attributable to malignancy. As a result of trial under-representation, patients with CKD may not be considered for cancer therapies that have potential to improve morbidity and mortality.

Also, most trials used serum creatinine or CrCl thresholds to exclude patients, despite data demonstrating that these are sub-optimal measures of kidney function in cancer patients. Given the availability of more accurate and validated methods for estimating kidney function, the oncology drugs trials cannot just rely on creatinine measurements.

Finally, two recent reviews published in NEJM and JAMA on immunotherapy related toxicities failed to mention renal toxicities. Liver and kidney are two organs that are responsible for most drug metabolisms. Ignoring those side effects is probably not a good idea. Space limitations and % incidence of renal incidence being low were cited reasons for not including renal toxicities.

As a renal community, it is important that we respond back and make sure the voice of the nephrologists is heard as more and more novel agents are in the market to treat cancer.  

Consult Rounds: Cisplatin induced AKI, can we predict?

Cisplatin is a well known nephrotoxic agent. But here is a scenario. You have a 51 y old man with no history of HTN, baseline serum creatinine of 1.1mg/dl, well nourished now diagnosed with laryngeal cancer. He is planned to get cisplatin. What is the risk of AKI post first dose of cisplatin for this individual?

Prediction models are helpful in such instances to guide the oncologists and nephrologists. Similar to the prediction of AKI and need for dialysis post contrast as done by Mehran et al, Motwani et al developed a prediction model for cisplatin based AKI.

The predictive model demonstrated reasonably good discrimination and calibration. The multivariate model was developed using a large cohort of patients and internally and externally validated. Its uses age, HTN, albumin and dose of cisplatin as the major coordinates.

Identification of high-risk individuals may facilitate appropriate preventative options such as more frequent laboratory monitoring, avoidance of concurrent use of other renal tubular toxins, and careful evaluation of dosing and administration of additional intravenous fluids. This study also suggests that baseline kidney function measured by creatinine may not be a good predictor of the risk of cisplatin induced AKI after the first course. 

I summarized the scoring the investigators designed and validated. 

Score Assigned	Age
0	<=60
1.5	61-70
2.5	71-90
	HTN
2	Yes
0	No

Score Assigned	Cisplatin Dose(mg)
0	<= 100
1	101-150
3	>=151
	Serum ALBUMIN(g/dl)
0	>3.5
2	1.3-3.5

So if score is 0-3 your risk of AKI is 3-8%, if score is 3.5-6, 15% and >6, risk is 28-39%

So in our case example, if the patient were to get 88mg of cisplatin and his albumin was 4.5g/dl, his risk scores for Cisplatin-AKI after the first course would be as follows: age < 60 years = 0; dose < 100 mg = 0; no hypertension = 0; and albumin > 3.5 g/dL = 0. Therefore, his total risk score would be 0 and his predicted probability of developing C-AKI would be 3%

Another example, A 69-year old man with a medical history of type 2 diabetes mellitus, hypertension, has new gastric cancer and is cisplatin-based adjuvant chemotherapy with a dose of 200 mg. His baseline creatinine is 1.0 mg/dL and her serum albumin is 2.8 g/dL. His risk scores for cisplatin AKI after the first course would be as follows: age 61 to 70 years = 1.5; hypertension = 2; dose > 150 mg = 3; albumin < 3.5 g/dL = 2. Therefore, his total risk score would be 8.5 and his predicted probability of developing AKI would be 28-39%.

A very helpful tool indeed for all of us to use.