Why does anemia cause pallor

Therefore, patients were included in the data analysis. Of these, were male and were female. Some characteristics of the study participants are presented in Table 1. The medical diagnoses of the patients are shown in Table 2. For pallor present, the likelihood ratio was 4.

For borderline cases, the likelihood ratio was 1. For pallor absent, the likelihood ratio was 0. The area under the ROC curve was 0. Observers B and C did not see patients together. Post hoc analysis of the operating characteristics of conjunctival pallor at different hemoglobin cutoffs are presented in Table 4. The likelihood ratio for pallor absent does not vary significantly for the different hemoglobin cutoffs. Although the accuracy of conjunctival pallor in the diagnosis of anemia has been examined by others, those studies had several important limitations.

Our study is different in that the sample was substantially larger, and patients of both genders were drawn from a racially heterogeneous population. Patients were not preselected for the study, and their medical diagnoses Table 2 were those that the internist would be likely to encounter in an ambulatory setting.

The larger sample allowed us to calculate likelihood ratios with smaller CIs. In addition, we defined pallor as a three-level variable, which we believe better reflects the spectrum of conjunctivae likely to be encountered. A physical sign such as conjunctival pallor that can provide information about the presence of anemia during patient evaluation might be helpful. To rule in anemia with confidence, the presence of conjunctival pallor should have a likelihood ratio that is greater than 10 for predicting anemia.

Although the finding of pale conjunctivae increases the probability of anemia, it does not permit a diagnosis of anemia, and there are few realistic situations in which the presence of pallor alone would allow the clinician to rule in anemia.

This probability may be sufficient to rule in the presence of anemia. This use of our data, however, should be approached with caution because these results were generated in a post hoc analysis and the CIs are wide 2. There are situations, however, in which the presence of pallor may be more helpful. For example, clinicians in the office often see patients whose probabilities of anemia are too low to justify ordering a hemoglobin determination to search for it.

Even when using a likelihood ratio of 4. Therefore, we conclude that finding pale conjunctivae in a patient without another reason for the patient to be anemic should lead the clinician to order a hemoglobin determination. To rule out anemia with confidence, conjunctival pallor should have a small likelihood ratio when pallor is absent. For example, a near normal or totally normal lung perfusion scan has a likelihood ratio of 0.

Although the absence of pallor revises the probability of anemia downward, we believe the change is not clinically meaningful because the change is insufficient to rule out disease. Presumably, a lower cutoff point for defining anemia should lead to a lower likelihood ratio for absent pallor. Although our post hoc analysis did show a decrease in the likelihood ratio from 0. Our study does not explain why patients with severe anemia did not always have pale conjunctivae. Alternatively, the observers in this study may not have been sufficiently skilled to detect pallor when it was present.

Our experience suggests that many conjunctivae are neither clearly pallid nor clearly normal, and it is likely that our three-level classification of pallor also enhanced agreement between observers. There are several limitations to this study. First, although the population was racially heterogeneous, data on ethnic and racial background were not recorded and analyzed.

Second, inexperienced medical students were among the evaluators in this study, although training and standardization were used to minimize their inexperience. Third, we studied only one possible sign for pallor. Pallor of the nail beds and palms are other signs that might have been studied. Fourth, we studied only inpatients, and our principal conclusion is directed at outpatients, although we do not know any reason why this discrepancy should be important.

This sign, however, without other information suggesting anemia, should be reason enough to order a hemoglobin determination. The absence of conjunctival pallor does not allow the clinician to rule out anemia, which means that physical diagnosis is not sufficient to exclude even severe anemia from consideration.

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Review provided by VeriMed Healthcare Network. Editorial team. Paleness can be caused by: Anemia blood loss , poor nutrition, or underlying disease Problems with the circulatory system Shock Fainting Frostbite Low blood sugar Chronic long-term diseases including infection and cancer Certain medicines Certain vitamin deficiencies.

When to Contact a Medical Professional. What to Expect at Your Office Visit. Your provider will examine you and ask about your medical history and symptoms, including: Did the paleness develop suddenly?

Did it happen after reminders of a traumatic event? Are you pale all over or only in one part of the body? If so, where? What other symptoms do you have? For example, do you have pain, shortness of breath , blood in the stool , or are you vomiting blood?