Demographic and Health Surveys Methodology - Measure DHS

B. Similarly, an adjustment is made for women who smoke (if information was collected). Theadjustment is to be made in accordance with the following table:Cigarettes SmokedAdjust Hb (g/dl)Concentration byNo adjustmentLess than 10 per day10–19 per day –0.320–39 per day –0.540 or more per day –0.7Unknown quantity or noncigarettessmokingC. The percentage anemic, by category, is obtained by dividing the numerators by the denominatorand multiplying the quotient by 100.Handling of Missing ValuesWomen who were not tested and women whose values were not recorded are excluded from both thedenominator and the numerators.Notes and ConsiderationsPregnancy causes an increase in blood fluid diluting somewhat the concentration of hemoglobin.Therefore the cutoff for mild anemia is lowered for pregnant women. No adjustment is made for thecutoff values for either moderate or severe anemia. Because the availability of oxygen is less at higheraltitudes (lower partial pressures) and because smoking interferes with the blood’s capacity to transferoxygen, adjustments need to be made for both altitude and smoking.People residing at higher altitudes (greater than 1,000 meters (3,300 feet)) have higher Hb and Hct levelsthan those residing at sea level. This variation is due to the lower oxygen partial pressure at higheraltitudes, a reduction in oxygen saturation of blood, and a compensatory increase in red cell production toensure adequate oxygen supply to the tissues. Thus, higher altitude causes a generalized upward shift ofthe Hb distributions. This shift may be associated with the underdiagnosis of anemia for residents ofhigher altitudes when sea-level cutoffs are applied (CDC, unpublished data). Therefore, the properdiagnosis of anemia for those residing at higher altitudes requires an upward adjustment of Hb cutoffs.The values for altitude-specific adjustment of Hb are derived from data collected by the CDC PediatricNutrition Surveillance System on children residing at various altitudes in the mountain states. Altitudeaffects Hb levels throughout pregnancy in a similar way (Chatfield, unpublished data).The influence of cigarette smoking is similar to that of altitude; smoking increases Hb level substantially.The higher Hb of smokers is a consequence of an increased carboxyhemoglobin from inhaling carbonmonoxide while smoking. Because carboxyhemoglobin has no oxygen-carrying capacity, its presencecauses a generalized upward shift of the Hb distribution curves (CDC, unpublished data). Therefore, asmoking-specific adjustment to the anemia cutoff is necessary for the proper diagnosis of anemia insmokers.The adjustment for altitude can be substantial, but the adjustment for smoking is less substantial. Thus,where no smoking information is available, no adjustment is made. However, altitude data should alwaysbe obtained to adjust where the altitude of the dwelling is more than 1,000 meters. Substitution of clusteraltitude is usually accepted instead of altitude for each dwelling in the cluster.–0.3Guide to DHS Statistics 141 Updated October 2012