The Effect of Financial Incentives on Patient Decisions to Undergo Low-value Head Computed Tomography Scans

BACKGROUND

Excessive diagnostic testing and defensive medicine contribute to billions of dollars in avoidable costs in the United States annually. Our objective was to determine the influence of financial incentives, accompanied with information regarding test risk and benefit, on patient preference for diagnostic testing.

METHODS

We conducted a cross-sectional survey of patients at the University of Michigan emergency department (ED). Each participant was presented with a hypothetical scenario involving an ED visit following minor traumatic brain injury. Participants were given information regarding potential benefit (detecting brain hemorrhage) and risk (developing cancer) of head computed tomography scan, as well as an incentive of $0 or $100 to forego testing. We used 0.1 and 1% for test benefit and risk, and values for risk, benefit, and financial incentive varied across participants. Our primary outcome was patient preference to undergo testing. We also collected demographic and numeracy information. We then used logistic regression to estimate odds ratios (ORs), which were adjusted for multiple potential confounders. Our sample size was designed to find at least 300 events (preference for testing) to allow for inclusion of up to 30 covariates in fully adjusted models. We had 85% to 90% power to detect a 10% absolute difference in testing rate across groups, assuming a 95% significance level.

RESULTS

We surveyed 913 patients. Increasing test benefit from 0.1% to 1% significantly increased test acceptance (adjusted OR [AOR] = 1.6, 95% confidence interval [CI] = 1.2 to 2.1) and increasing test risk from 0.1% to 1% significantly decreased test acceptance (AOR = 0.70, 95% CI = 0.52 to 0.93). Finally, a $100 incentive to forego low-value testing significantly reduced test acceptance (AOR = 0.6; 95% CI = 0.4 to 0.8).

CONCLUSIONS

Providing financial incentives to forego testing significantly decreased patient preference for testing, even when accounting for test benefit and risk. This work is preliminary and hypothetical and requires confirmation in larger patient cohorts facing these actual decisions.

Patient Preferences for Diagnostic Testing in the Emergency Department: A Cross-sectional Study

BACKGROUND

Diagnostic testing is common during emergency department (ED) visits. Little is understood about patient preferences for such testing. We hypothesized that a patient's willingness to undergo diagnostic testing is influenced by the potential benefit, risk, and personal cost.

METHODS

We conducted a cross sectional survey among ED patients for diagnostic testing in two hypothetical scenarios: chest pain (CP) and mild traumatic brain injury (mTBI). Each scenario defined specific risks, benefits, and costs of testing. The odds of a participant desiring diagnostic testing were calculated using a series of nested multivariable logistic regression models.

RESULTS

Participants opted for diagnostic testing 68.2% of the time, including 69.7% of CP and 66.7% of all mTBI scenarios. In the CP scenario, 81% of participants desired free testing versus 59% when it was associated with a $100 copay (difference = 22%, 95% confidence interval [CI] = 16% to 28%). Similarly, in the mTBI scenario, 73% of adult participants desired free testing versus 56% when charged a $100 copayment (difference = 17%, 95% CI = 11% to 24%). Benefit and risk had mixed effects across the scenarios. In fully adjusted models, the association between cost and desire for testing persisted in the CP (odds ratio [OR] = 0.33, 95% CI = 0.23 to 0.47) and adult mTBI (OR = 0.47, 95% CI = 0.33 to 0.67) scenarios.

CONCLUSIONS

In this ED-based study, patient preferences for diagnostic testing differed significantly across levels of risk, benefit, and cost of diagnostic testing. Cost was the strongest and most consistent factor associated with decreased desire for testing.

Whole exome sequencing identifies causative mutations in the majority of consanguineous or familial cases with childhood-onset increased renal echogenicity

Chronically increased echogenicity on renal ultrasound is a sensitive early finding of chronic kidney disease that can be detected before manifestation of other symptoms. Increased echogenicity, however, is not specific for a certain etiology of chronic kidney disease. Here, we performed whole exome sequencing in 79 consanguineous or familial cases of suspected nephronophthisis in order to determine the underlying molecular disease cause. In 50 cases, there was a causative mutation in a known monogenic disease gene. In 32 of these cases whole exome sequencing confirmed the diagnosis of a nephronophthisis-related ciliopathy. In 8 cases it revealed the diagnosis of a renal tubulopathy. The remaining 10 cases were identified as Alport syndrome (4), autosomal-recessive polycystic kidney disease (2), congenital anomalies of the kidney and urinary tract (3), and APECED syndrome (1). In 5 families, in whom mutations in known monogenic genes were excluded, we applied homozygosity mapping for variant filtering, and identified 5 novel candidate genes (RBM48, FAM186B, PIAS1, INCENP, and RCOR1) for renal ciliopathies. Thus, whole exome sequencing allows the detection of the causative mutation in 2/3 of affected individuals, thereby presenting the etiologic diagnosis and allows identification of novel candidate genes.

SDCCAG8 Interacts with RAB Effector Proteins RABEP2 and ERC1 and Is Required for Hedgehog Signaling

Recessive mutations in the SDCCAG8 gene cause a nephronophthisis-related ciliopathy with Bardet-Biedl syndrome-like features in humans. Our previous characterization of the orthologous Sdccag8^gt/gt mouse model recapitulated the retinal-renal disease phenotypes and identified impaired DNA damage response signaling as an underlying disease mechanism in the kidney. However, several other phenotypic and mechanistic features of Sdccag8^gt/gt mice remained unexplored. Here we show that Sdccag8^gt/gt mice exhibit developmental and structural abnormalities of the skeleton and limbs, suggesting impaired Hedgehog (Hh) signaling. Indeed, cell culture studies demonstrate the requirement of SDCCAG8 for ciliogenesis and Hh signaling. Using an affinity proteomics approach, we demonstrate that SDCCAG8 interacts with proteins of the centriolar satellites (OFD1, AZI1), of the endosomal sorting complex (RABEP2, ERC1), and with non-muscle myosin motor proteins (MYH9, MYH10, MYH14) at the centrosome. Furthermore, we show that RABEP2 localization at the centrosome is regulated by SDCCAG8. siRNA mediated RABEP2 knockdown in hTERT-RPE1 cells leads to defective ciliogenesis, indicating a critical role for RABEP2 in this process. Together, this study identifies several centrosome-associated proteins as novel SDCCAG8 interaction partners, and provides new insights into the function of SDCCAG8 at this structure.

A FANCD2/FANCI-Associated Nuclease 1-Knockout Model Develops Karyomegalic Interstitial Nephritis

Karyomegalic interstitial nephritis (KIN) is a chronic interstitial nephropathy characterized by tubulointerstitial nephritis and formation of enlarged nuclei in the kidneys and other tissues. We recently reported that recessive mutations in the gene encoding FANCD2/FANCI-associated nuclease 1 (FAN1) cause KIN in humans. FAN1 is a major component of the Fanconi anemia-related pathway of DNA damage response (DDR) signaling. To study the pathogenesis of KIN, we generated a Fan1 knockout mouse model, with abrogation of Fan1 expression confirmed by quantitative RT-PCR. Challenging Fan1^-/- and wild-type mice with 20 mg/kg cisplatin caused AKI in both genotypes. In contrast, chronic injection of cisplatin at 2 mg/kg induced KIN that led to renal failure within 5 weeks in Fan1^-/- mice but not in wild-type mice. Cell culture studies showed decreased survival and reduced colony formation of Fan1^-/- mouse embryonic fibroblasts and bone marrow mesenchymal stem cells compared with wild-type counterparts in response to treatment with genotoxic agents, suggesting that FAN1 mutations cause chemosensitivity and bone marrow failure. Our data show that Fan1 is involved in the physiologic response of kidney tubular cells to DNA damage, which contributes to the pathogenesis of CKD. Moreover, Fan1^-/- mice provide a new model with which to study the pathomechanisms of CKD.

FAT1 mutations cause a glomerulotubular nephropathy

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linking FAT1 and RAC1/CDC42 to podocyte and tubular cell function.

Large-scale targeted sequencing comparison highlights extreme genetic heterogeneity in nephronophthisis-related ciliopathies

BACKGROUND

The term nephronophthisis-related ciliopathies (NPHP-RC) describes a group of rare autosomal-recessive cystic kidney diseases, characterised by broad genetic and clinical heterogeneity. NPHP-RC is frequently associated with extrarenal manifestations and accounts for the majority of genetically caused chronic kidney disease (CKD) during childhood and adolescence. Generation of a molecular diagnosis has been impaired by this broad genetic heterogeneity. However, recently developed high-throughput exon sequencing techniques represent powerful and efficient tools to screen large cohorts for dozens of causative genes.

METHODS

Therefore, we performed massively multiplexed targeted sequencing using the modified molecular inversion probe strategy (MIPs) in an international cohort of 384 patients diagnosed with NPHP-RC.

RESULTS

As a result, we established the molecular diagnoses in 81/384 unrelated individuals (21.1%). We detected 127 likely disease-causing mutations in 18 of 34 evaluated NPHP-RC genes, 22 of which were novel. We further compared a subgroup of current findings to the results of a previous study in which we used an array-based microfluidic PCR technology in the same cohort. While 78 likely disease-causing mutations were previously detected by the array-based microfluidic PCR, the MIPs approach identified 94 likely pathogenic mutations. Compared with the previous approach, MIPs redetected 66 out of 78 variants and 28 previously unidentified variants, for a total of 94 variants.

CONCLUSIONS

In summary, we demonstrate that the modified MIPs technology is a useful approach to screen large cohorts for a multitude of established NPHP genes in order to identify the underlying molecular cause. Combined application of two independent library preparation and sequencing techniques, however, may still be indicated for Mendelian diseases with extensive genetic heterogeneity in order to further increase diagnostic sensitivity.

Targeted Resequencing of 29 Candidate Genes and Mouse Expression Studies Implicate ZIC3 and FOXF1 in Human VATER/VACTERL Association

The VATER/VACTERL association describes the combination of congenital anomalies including vertebral defects, anorectal malformations, cardiac defects, tracheoesophageal fistula with or without esophageal atresia, renal malformations, and limb defects. As mutations in ciliary genes were observed in diseases related to VATER/VACTERL, we performed targeted resequencing of 25 ciliary candidate genes as well as disease-associated genes (FOXF1, HOXD13, PTEN, ZIC3) in 123 patients with VATER/VACTERL or VATER/VACTERL-like phenotype. We detected no biallelic mutation in any of the 25 ciliary candidate genes; however, identified an identical, probably disease-causing ZIC3 missense mutation (p.Gly17Cys) in four patients and a FOXF1 de novo mutation (p.Gly220Cys) in a further patient. In situ hybridization analyses in mouse embryos between E9.5 and E14.5 revealed Zic3 expression in limb and prevertebral structures, and Foxf1 expression in esophageal, tracheal, vertebral, anal, and genital tubercle tissues, hence VATER/VACTERL organ systems. These data provide strong evidence that mutations in ZIC3 or FOXF1 contribute to VATER/VACTERL.

IFT81, encoding an IFT-B core protein, as a very rare cause of a ciliopathy phenotype

Background

Bidirectional intraflagellar transport (IFT) consists of two major protein complexes, IFT-A and IFT-B. In contrast to the IFT-B complex, all components of IFT-A have recently been linked to human ciliopathies when defective. We therefore hypothesised that mutations in additional IFT-B encoding genes can be found in patients with multisystemic ciliopathies.

Methods

We screened 1628 individuals with reno-ocular ciliopathies by targeted next-generation sequencing of ciliary candidate genes, including all IFT-B encoding genes.

Results

Consequently, we identified a homozygous mutation in IFT81 affecting an obligatory donor splice site in an individual with nephronophthisis and polydactyly. Further, we detected a loss-of-stop mutation with extension of the deduced protein by 10 amino acids in an individual with neuronal ceroid lipofuscinosis-1. This proband presented with retinal dystrophy and brain lesions including cerebellar atrophy, a phenotype to which the IFT81 variant might contribute. Cultured fibroblasts of this latter affected individual showed a significant decrease in ciliated cell abundance compared with controls and increased expression of the transcription factor GLI2 suggesting deranged sonic hedgehog signalling.

Conclusions

This work describes identification of mutations of IFT81 in individuals with symptoms consistent with the clinical spectrum of ciliopathies. It might represent the rare case of a core IFT-B complex protein found associated with human disease. Our data further suggest that defects in the IFT-B core are an exceedingly rare finding, probably due to its indispensable role for ciliary assembly in development.

TMEM231, mutated in orofaciodigital and Meckel syndromes, organizes the ciliary transition zone

TMEM231, a functional component of the MKS complex at the ciliary transition zone, is mutated in orofaciodigital syndrome type 3 and Meckel syndrome.

The Meckel syndrome (MKS) complex functions at the transition zone, located between the basal body and axoneme, to regulate the localization of ciliary membrane proteins. We investigated the role of Tmem231, a two-pass transmembrane protein, in MKS complex formation and function. Consistent with a role in transition zone function, mutation of mouse Tmem231 disrupts the localization of proteins including Arl13b and Inpp5e to cilia, resulting in phenotypes characteristic of MKS such as polydactyly and kidney cysts. Tmem231 and B9d1 are essential for each other and other complex components such as Mks1 to localize to the transition zone. As in mouse, the Caenorhabditis elegans orthologue of Tmem231 localizes to and controls transition zone formation and function, suggesting an evolutionarily conserved role for Tmem231. We identified TMEM231 mutations in orofaciodigital syndrome type 3 (OFD3) and MKS patients that compromise transition zone function. Thus, Tmem231 is critical for organizing the MKS complex and controlling ciliary composition, defects in which cause OFD3 and MKS.

DCDC2 mutations cause a renal-hepatic ciliopathy by disrupting Wnt signaling

Nephronophthisis-related ciliopathies (NPHP-RC) are recessive diseases characterized by renal dysplasia or degeneration. We here identify mutations of DCDC2 as causing a renal-hepatic ciliopathy. DCDC2 localizes to the ciliary axoneme and to mitotic spindle fibers in a cell-cycle-dependent manner. Knockdown of Dcdc2 in IMCD3 cells disrupts ciliogenesis, which is rescued by wild-type (WT) human DCDC2, but not by constructs that reflect human mutations. We show that DCDC2 interacts with DVL and DCDC2 overexpression inhibits β-catenin-dependent Wnt signaling in an effect additive to Wnt inhibitors. Mutations detected in human NPHP-RC lack these effects. A Wnt inhibitor likewise restores ciliogenesis in 3D IMCD3 cultures, emphasizing the importance of Wnt signaling for renal tubulogenesis. Knockdown of dcdc2 in zebrafish recapitulates NPHP-RC phenotypes, including renal cysts and hydrocephalus, which is rescued by a Wnt inhibitor and by WT, but not by mutant, DCDC2. We thus demonstrate a central role of Wnt signaling in the pathogenesis of NPHP-RC, suggesting an avenue for potential treatment of NPHP-RC.

Fourteen monogenic genes account for 15% of nephrolithiasis/nephrocalcinosis

Nephrolithiasis is a prevalent condition with a high morbidity. Although dozens of monogenic causes have been identified, the fraction of single-gene disease has not been well studied. To determine the percentage of cases that can be molecularly explained by mutations in 1 of 30 known kidney stone genes, we conducted a high-throughput mutation analysis in a cohort of consecutively recruited patients from typical kidney stone clinics. The cohort comprised 272 genetically unresolved individuals (106 children and 166 adults) from 268 families with nephrolithiasis (n=256) or isolated nephrocalcinosis (n=16). We detected 50 likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 14.9% (40 of 268) of all cases; 20 of 50 detected mutations were novel (40%). The cystinuria gene SLC7A9 (n=19) was most frequently mutated. The percentage of monogenic cases was notably high in both the adult (11.4%) and pediatric cohorts (20.8%). Recessive causes were more frequent among children, whereas dominant disease occurred more abundantly in adults. Our study provides an in-depth analysis of monogenic causes of kidney stone disease. We suggest that knowledge of the molecular cause of nephrolithiasis and nephrocalcinosis may have practical implications and might facilitate personalized treatment.

Mutations in SPAG1 cause primary ciliary dyskinesia associated with defective outer and inner dynein arms

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, autosomal-recessive disorder, characterized by oto-sino-pulmonary disease and situs abnormalities. PCD-causing mutations have been identified in 20 genes, but collectively they account for only ∼65% of all PCDs. To identify mutations in additional genes that cause PCD, we performed exome sequencing on three unrelated probands with ciliary outer and inner dynein arm (ODA+IDA) defects. Mutations in SPAG1 were identified in one family with three affected siblings. Further screening of SPAG1 in 98 unrelated affected individuals (62 with ODA+IDA defects, 35 with ODA defects, 1 without available ciliary ultrastructure) revealed biallelic loss-of-function mutations in 11 additional individuals (including one sib-pair). All 14 affected individuals with SPAG1 mutations had a characteristic PCD phenotype, including 8 with situs abnormalities. Additionally, all individuals with mutations who had defined ciliary ultrastructure had ODA+IDA defects. SPAG1 was present in human airway epithelial cell lysates but was not present in isolated axonemes, and immunofluorescence staining showed an absence of ODA and IDA proteins in cilia from an affected individual, thus indicating that SPAG1 probably plays a role in the cytoplasmic assembly and/or trafficking of the axonemal dynein arms. Zebrafish morpholino studies of spag1 produced cilia-related phenotypes previously reported for PCD-causing mutations in genes encoding cytoplasmic proteins. Together, these results demonstrate that mutations in SPAG1 cause PCD with ciliary ODA+IDA defects and that exome sequencing is useful to identify genetic causes of heterogeneous recessive disorders.

High-throughput mutation analysis in patients with a nephronophthisis-associated ciliopathy applying multiplexed barcoded array-based PCR amplification and next-generation sequencing

OBJECTIVE

To identify disease-causing mutations within coding regions of 11 known NPHP genes (NPHP1-NPHP11) in a cohort of 192 patients diagnosed with a nephronophthisis-associated ciliopathy, at low cost.

METHODS

Mutation analysis was carried out using PCR-based 48.48 Access Array microfluidic technology (Fluidigm) with consecutive next-generation sequencing. We applied a 10-fold primer multiplexing approach allowing PCR-based amplification of 475 amplicons (251 exons) for 48 DNA samples simultaneously. After four rounds of amplification followed by indexing all of 192 patient-derived products with different barcodes in a subsequent PCR, 2 × 100 paired-end sequencing was performed on one lane of a HiSeq2000 instrument (Illumina). Bioinformatics analysis was performed using 'CLC Genomics Workbench' software. Potential mutations were confirmed by Sanger sequencing and shown to segregate.

RESULTS

Bioinformatics analysis revealed sufficient coverage of 30 × for 168/192 (87.5%) DNA samples (median 449 ×) and of 234 out of 251 targeted coding exons (sensitivity: 93.2%). For proof-of-principle, we analysed 20 known mutations and identified 18 of them in the correct zygosity state (90%). Likewise, we identified pathogenic mutations in 34/192 patients (18%) and discovered 23 novel mutations in the genes NPHP3 (7), NPHP4 (3), IQCB1 (4), CEP290 (7), RPGRIP1L (1), and TMEM67 (1). Additionally, we found 40 different single heterozygous missense variants of unknown significance.

CONCLUSIONS

We conclude that the combined approach of array-based multiplexed PCR-amplification on a Fluidigm Access Array platform followed by next-generation sequencing is highly cost-efficient and strongly facilitates diagnostic mutation analysis in broadly heterogeneous Mendelian disorders.