Variation in the Diagnosis of Child Abuse in Severely Injured Infants

METHODS

The Kids’ Inpatient Database 1997 was developed as part of the Healthcare Cost and Utilization Project (HCUP) to facilitate the study of a wide range of pediatric disorders.¹¹ The data set includes information concerning aspects of hospital care and patient outcomes of children ≤18 years old from a sample of hospitals across the United States in 1997. Pediatric discharges were sampled from the following 22 states: Arizona, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Iowa, Illinois, Kansas, Maryland, Massachusetts, Missouri, New Jersey, New York, Oregon, Pennsylvania, South Carolina, Tennessee, Utah, Washington, and Wisconsin.

The sample of discharge information was collected from 2521 hospitals and included 1.9 million discharge records. These hospitals included general community hospitals, academic medical centers, and pediatric hospitals. A systematic random sample was drawn from these hospitals consisting of 10% of births and 80% of other pediatric discharges. Once weighted to account for sampling based on HCUP methodology,¹² the national estimates represented >6.5 million discharges. Patient-level data (age, gender, insurance status, diagnosis, and external cause of injury codes based on International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] codes) and hospital-level factors (teaching status, National Association of Children’s Hospitals and Related Institutions [NACHRI] hospital type, and hospital bed size) were analyzed in this study.

Subjects

From the original data set, we extracted 2253 weighted cases of patients <1 year old with TBI and femur fracture (ICD-9-CM codes: 820.00–821.39) (Fig 1). TBI included all intracranial injury (ICD-9-CM codes: 800.10–800.49, 800.60–800.99, 801.10–801.49, 801.60–801.99, 803.10–803.49, 803.60–803.99, 804.10–804.49, 804.60–804.99, 851.00–854.19, and 950.00–953.9). Children were excluded if they were not admitted through the emergency department (to avoid counting hospital transfers or referrals for specialty care); if they were injured by a motor vehicle, a gunshot, or a knife stabbing; if they did not have any E code assigned; or if they did not have sufficient data available to calculate an injury severity score (ISS).

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FIGURE 1

Patient inclusion/exclusion flowchart.

RESULTS

The largest group of patients (49%) was admitted to general hospitals, one fourth was admitted to general hospitals with children’s units, and the remaining one fourth was admitted to a children’s hospital (Table 1). Children who were treated at children’s hospitals tended to be younger, more severely injured, and more likely to have private health insurance than those cared for at general hospitals. General hospitals cared for a smaller proportion of children with TBI but a greater proportion of femur fractures than the other 2 hospital types.

The rate of identification of child abuse diagnosis varied widely between the hospital types. Child abuse was identified more often when there was more pediatric specialty care available. Children’s hospitals had the highest rates of identified child abuse, with the diagnosis being made more than twice as often as in general hospitals (29% vs 13%; P < .05). General hospitals with a children’s unit had more abuse identified than general hospitals without a children’s unit but less than a children’s hospital. Falls, as a proffered cause of injury, remained fairly constant between groups, ranging from 60% in children’s hospitals to 69% in general hospitals (P < .05).

Nearly all the hospitals in this cohort were in urban settings. Half of the general hospitals were teaching facilities, as opposed to nearly three fourths of the children’s hospitals. Most hospitals were distributed fairly evenly across the United States. The majority of general hospitals were reported as large, whereas more than half of the children’s hospitals were categorized as small.

The proportion of children who were diagnosed with child abuse varied between hospital types after stratifying by injury (Table 2). Patients with all types of intracranial lesions were identified as victims of child abuse least frequently in general hospitals and most frequently in children’s hospitals. This pattern persisted with lesions more suspicious of abuse. In children with a subdural or epidural hemorrhage with skull fractures, ∼10% were identified in general hospitals as abused, and nearly one third were identified in children’s hospitals as abused. Infants with subdural hemorrhage without skull fractures were most likely to be diagnosed as having been abused. These included nearly one half of the infants with this condition admitted to general hospitals and three fourths of infants admitted to children’s hospitals. Children with femur fractures were identified as abuse victims in a similar pattern as intracranial injury, least frequently in general hospitals and most frequently in children’s hospitals. In all injury groups, general hospitals with a children’s unit identified abuse more frequently than general hospitals without a children’s unit but less frequently than children’s hospitals.

A reduced regression model showed that hospital type was associated with increased odds of receiving an abuse diagnosis. Infants admitted to children’s hospitals had a 2.7-fold (95% CI: 2.1 to 3.5) increased odds of being diagnosed with child abuse compared with infants admitted to general hospitals. This difference persisted after controlling for patient and hospital factors (odds ratio [OR]: 2.7; 95% CI: 2.0 to 3.6). Hospital teaching status did not significantly confound or interact with hospital type. Infants admitted to general hospitals with a children’s unit had increased odds (OR: 1.6; 95% CI: 1.2 to 2.2) of receiving a child abuse diagnosis compared with those at general hospitals without a children’s unit, but this trend was no longer significant after adjustment (OR: 1.3; 95% CI: 0.9 to 1.7). When we controlled for patients who were discharged from the hospital to another facility, we found that the OR comparing child abuse diagnosis in children’s hospitals with that observed in general hospitals increased slightly, from 2.7 to 3.2. There was no change in ORs for general hospitals with a children’s unit when controlling for transferred patients.

An estimate was obtained of the number of children who would have been diagnosed as abused if the rate of diagnosis of abuse observed seen at children’s hospitals was applied to all hospitals (Table 3). The c statistic of the reference model of children diagnosed with abuse at children’s hospitals was 0.851. The mean discrepancy for children not diagnosed as abused at general hospitals without children’s units was −10.5% (95% CI: −13.2 to −7.8), showing that an additional 10.5% (114) of these children had characteristics similar to the abused children seen at children’s hospitals. The total number of children diagnosed with abuse at general hospitals without a children’s unit would be 257 (23.6%). General hospitals with a children’s unit had a mean discrepancy rate of −10.8% (95% CI: −15.1 to −6.5), yielding an additional 64 abuse cases. The total number of missed cases of abuse with these 2 specific injury types was 178, which corresponds to nearly 40% of all total cases of abuse among infants under 1 year of age with these 2 specific injury types.

DISCUSSION

In this population-based study of 2253 weighted cases of infants who were hospitalized with either a femur fracture or TBI, we explored the proportion of patients diagnosed with child abuse among different hospital types. Infants seen in children’s hospitals tended to be younger, were more severely injured, and were more likely to be covered by private insurance than children who were cared for at general hospitals. Infants admitted to general hospitals for severe injuries were diagnosed as abused only half as frequently as those admitted to children’s specialty hospitals. This pattern persisted even for the injury most frequently diagnosed as abuse-related: subdural hemorrhage without skull fracture. Using the practice pattern of children’s hospitals as the reference group, an additional 178 cases of abuse would have been diagnosed across the United States in 1997 in this cohort of severely injured infants with these 2 specific injury patterns.

Our study found a large variation in the frequency of diagnosis of abuse based on NACHRI hospital type. Hospitals that focused exclusively on pediatric patients were more likely to detect and report child abuse; this discrepancy was not explained by the patient’s age, injury severity, or insurance status. This pattern was noted in all injury patterns evaluated. There are several potential explanations for this difference. It is possible that injured children were preferentially evaluated and admitted to children’s hospitals simply because they were suspected to have been abused. Additionally, more severely injured children may be preferentially evaluated for abuse in children’s hospitals because children’s hospitals care for more severely injured children than general hospitals. ICD-9 E codes may not be an accurate method of determining population-based estimates for any diagnosis or condition. To help reduce these biases, we excluded all patients who were transferred between facilities, thereby reducing the possibility that more complex cases would be cared for at specialty centers. We also controlled for patients who were discharged from the hospital to another facility and did not find considerable changes in the ORs of the final model. Although children’s hospitals cared for more severely injured children (as measured by the abbreviated injury score), the discrepancy in frequency of diagnosis of abuse remained after injury severity was accounted for in the statistical analysis. Nonchildren’s hospitals had a lower rate of E coding and therefore had a higher proportion of cases excluded from the study.

The definitive diagnosis of child abuse is difficult to ascertain; this study used the clinical diagnosis of child abuse as defined by each participating institution. This clinical diagnosis may well be incorrect, and this study may be subject to misclassification bias in that nonabused patients may have been categorized as abused and truly abused patients may never have been considered to be abuse victims. Previous studies have identified a tendency to underdiagnose child abuse⁵,⁶; therefore, it may be reasonable to assume that more abused patients were misclassified as not abused than nonabused patients were labeled as abused. It is encouraging to note that previous studies suggest that the true rate of child abuse more closely approximates the rate detected at children’s hospitals. Hettler and Greenes¹³ found that 30% of children 0 to 3 years old with acute traumatic intracranial injury were victims of abuse. Reece and Sege² described 50% of subdural hemorrhages resulting from abuse, and Billmire and Myers¹⁴ reported that 92% of intracranial bleeds without skull fractures in children under 1 year of age were the result of abuse. Femur fractures have also been described to be the result of abuse in rates similar to that of children’s hospitals.¹⁵,¹⁶ The most likely explanation for the observed difference in the likelihood of reaching a diagnosis of child abuse seems to be a systematic underdiagnosis of child abuse at general hospitals.

Several studies have highlighted the danger of missing an abusive etiology among injured children. Child abuse is often a chronic condition that recurs until the victim and perpetrator are no longer in contact. One of the late cardinal signs of abuse is multiple wounds or fractures in various stages of healing. Several case series of child abuse show that 18% to 80% of abused children show some signs of prior abuse.³,¹⁷–¹⁹ These abused children most likely saw a physician at some point before receiving the diagnosis of abuse but were not diagnosed appropriately. Jenny et al⁵ reported that 31% of abused patients admitted with acute head injuries had been recently evaluated by physicians for complaints consistent with acute head injury and were incorrectly diagnosed. The most common erroneous diagnoses were viral gastroenteritis followed by accidental head injury and ruled-out sepsis.

Dalton et al⁶ reported that in a cohort of children <3 years old with femur fractures, 20% of the fractures resulting from abuse were diagnosed at a later date, well after the initial hospitalization. Other case reports of misdiagnosed child abuse have been published.²⁰,²¹

Although the process of identifying and reporting suspected child abuse is complex, recent reports have highlighted the importance of specific continuing medical education. In a cohort of primary care pediatricians, Flaherty et al⁷ identified both patient and physician factors that are associated with increased frequency of suspecting abuse as a mechanism of injury. The only practitioner-level factor associated with increased frequency of suspicion of abuse was recent physician education about child abuse. In another report, Flaherty et al²² described a 10-fold increase in physicians reporting child abuse when they had been exposed to abuse-specific continuing medical education. A study of military physicians showed that, although pediatricians had a similar amount of child maltreatment training in residency to emergency physicians, pediatricians reported a significantly greater amount of continuing medical education in abuse than other specialties after residency.⁸ The only factor associated with increased reporting of child abuse in that cohort was the presence of postgraduate abuse training. If this pattern were true among civilian doctors, one might reasonably suppose that one factor in the underdiagnosis of child abuse in general hospitals might be the result of lower levels of abuse-specific continuing medical education.

The quantitative burden of the underdiagnosis of child abuse is likely to be substantial, because the majority of children are cared for at general hospitals with or without pediatric units. Even among this cohort of severely injured infants, general hospitals cared for the largest proportion of patients. Hospital emergency departments are complex environments and are likely to require quality-improvement programs to ensure that not only are clinical staff trained in the recognition of abuse but also that systems are in place to support the identification, medical and social evaluation, and management of abused infants.