Case Definition
Case Classification and Severity Criteria
Acute idiopathic pulmonary hemorrhage (AIPH) is the sudden onset of pulmonary hemorrhage in a previously healthy infant in whom differential diagnoses and neonatal medical problems that might cause pulmonary hemorrhage have been ruled out. Pulmonary hemorrhage can appear as hemoptysis or blood in the nose or airway with no evidence of upper respiratory or gastrointestinal bleeding. Patients have acute, severe respiratory distress or failure, requiring mechanical ventilation and chest radiograph (CXR), and usually demonstrate bilateral infiltrates.
AIPH among infants and sudden infant death syndrome (SIDS) potentially share similar risk factors (e.g., age group and maternal cigarette smoking). Also, in certain cases, SIDS is associated with pulmonary hemorrhage found at autopsy. Thus, factors that are known risk factors for SIDS should be identified when evaluating an infant possibly having AIPH. Potential information sources for case-identification and case-status classification during an investigation of pulmonary hemorrhage are provided in Table 1 of the original guideline document.
Clinically Confirmed Cases of AIPH Among Infants
Criteria for a confirmed case include pulmonary hemorrhage in a previously healthy infant aged <1 year with a gestational age of >32 weeks, with no history of neonatal medical problems that might cause pulmonary hemorrhage, and whose condition meets all of the following three criteria:
- Abrupt or sudden onset of overt bleeding or obvious evidence of blood in the airway, including
- epistaxis, hemoptysis, or frank blood in the airway below the larynx at visualization, not caused by any medical procedure (e.g., laryngoscopy or intubation);
or
- identification of hemosiderin-laden macrophages (>20% of pulmonary macrophages containing hemosiderin on bronchoalveolar lavage or biopsy specimen). A source of bleeding from the nose and oropharynx should be ruled out at the time of admission.
- Severe-appearing illness leading to acute respiratory distress or respiratory failure, resulting in hospitalization in a pediatric intensive care unit (PICU) or neonatal intensive care unit (NICU) with intubation and mechanical ventilation.
- Diffuse unilateral or bilateral pulmonary infiltrates visible on CXR or computerized tomography (CT) of the chest. CXR or chest CT findings should be documented within 48 hours of examination of the infant.
A previously healthy infant should
- have been discharged from the hospital after birth with an uneventful course before the occurrence of bronchoalveolar hemorrhage;
- never have been previously intubated, nor required respiratory support with oxygen;
- not have evidence of physical abuse;
- not have any abnormality identified on admission or follow-up bronchoscopy that would explain the bleeding; and
- not have neonatal medical problems that can cause pulmonary hemorrhage.
The Centers for Disease Control and Prevention (CDC) will adhere closely to this case definition, requiring that all the criteria be met for a confirmed case. The definition for a clinically confirmed case excludes pulmonary hemorrhage among older children and infants with restricted access to a PICU. Because no criteria exist for postmortem examinations, this definition excludes infants who die before hospital and PICU admission, whose illness might have met the case definition. However, the definitions for probable and suspect cases (see the following) will capture the majority of these cases and allow identification of illness among infants who die before examination by a physician.
Probable Cases of AIPH Among Infants
Criteria for a probable case include a previously healthy infant aged <1 year with a gestational age of >32 weeks,
- who has a sudden onset of bleeding from the airway, with or without respiratory distress, with or without intubation, and with or without pulmonary infiltrates on CXR or chest CT;
or
- who died and had evidence of bleeding from the airway found on autopsy or postmortem; had been in respiratory distress; would or should have been intubated in the opinion of a clinician; and would have had infiltrates on CXR or chest CT.
Suspected Cases of AIPH Among Infants
Criteria for a suspected case include a previously healthy infant,
- who died and had evidence of bleeding from the airway found on autopsy or postmortem;
or
- who either did not have chest imaging studies or had imaging studies that indicated no pulmonary infiltrates.
Respiratory distress or intubation is not required for a suspected case.
Severity Classification Scheme for AIPH Among Infants
Because of the potential for variation in symptoms among infants for each of the criteria, different case combinations might be related to the timing or duration of symptoms, disease severity, pathologic processes, or etiologic agents associated with AIPH among infants. A discussion of the proposed case-classification categories for AIPH among infants is provided in Tables 2 and 3 in the original guideline document.
A summary of clinical features of AIPH among infants and neonatal medical problems and differential diagnoses that should be ruled out before classifying a case as AIPH among infants are included in the original guideline document. Other differential diagnoses associated with pulmonary hemorrhage are also listed in the original guideline document.
Feasibility Study To Determine the Concordance of International Classification of Disease (ICD) Codes for Pulmonary Hemorrhage with the CDC Case Definition
CDC will retrospectively review cases of pulmonary hemorrhage to determine the public health impact of AIPH among infants and to generate hypotheses regarding the importance of risk factors possibly associated with AIPH among infants. If that review indicates that AIPH among infants is a separate clinical entity and that these cases have occurred in clusters, or that an increase in incidence or mortality is associated with these cases, CDC will initiate prospective surveillance and case ascertainment to identify cases for epidemiologic studies designed to confirm or disprove associations between pulmonary hemorrhage host factors, environmental factors, and biologic agents, including such molds as Stachybotrys chartarum.
Retrospective Review by Using Existing Data Sources
Refer to the original guideline document for a discussion of retrospective reviews that have been performed by CDC, possible benefits of retrospective review of AIPH, and the CDC’s plan for retrospective review.
Investigation of Suspected Clusters of AIPH Among Infants
If an apparent cluster of cases of pulmonary hemorrhage occurs, CDC recommends that state health departments initiate an investigation. CDC staff will work with each state, upon request, to evaluate case reports to assist the epidemiologic and environmental investigation, if any. State health departments can use existing protocols for outbreak or cluster investigations and collect information to determine if cases meet the CDC case definition for AIPH among infants. Because these cases probably will be identified in pediatric intensive care units (PICUs), CDC recommends that if the PICU staff identifies any suspected cases, they report them to their state epidemiologist.
For each case of AIPH in an infant, CDC recommends that PICU and NICU staff collect clinical information to certify case status, demographic information, and reports regarding the status of the patient's home. PICU and NICU staff also should carefully document illnesses that are similar clinically to AIPH, even if another specific etiology is confirmed, because they might offer additional information or indicate the need to re-assess the case definition.
If performed, environmental assessment of the home to gather pertinent risk-assessment data should use standard protocols designed by trained environmental health professionals. At a minimum, the assessment should involve visual inspection, including checks for dampness, water damage, obvious mold, evidence of pests, and environmental tobacco smoke. Depending on the assessed need for further evaluation and the resources available, additional investigation might include determining moisture content, settled dust sampling, air sampling for different allergens and biologically active compounds, and other investigations as needed.
