▁inject ed ▁P PD ▁equivalent ▁to ▁ 1 0 0 , 0 0 0 ▁units ▁per ▁m l ▁to ▁the ▁skin ▁over ▁the ▁flex or ▁surface ▁of ▁the ▁left ▁for ear m ▁in ▁a ▁circular ▁pattern ▁of ▁six . ▁The ▁test ▁was ▁read ▁between ▁two ▁and ▁seven ▁days ▁later . ▁The ▁injection ▁could ▁not ▁be ▁into ▁sites ▁containing ▁super f icial ▁ve ins . ▁ ▁The ▁reading ▁of ▁the ▁He af ▁test ▁was ▁defined ▁by ▁a ▁scale : ▁ ▁Neg ative ▁- ▁No ▁ind uration , ▁maybe ▁six ▁minute ▁pun ct ure ▁sc ars ▁Gra de ▁ 1 ▁- ▁four ▁to ▁six ▁pap ules ▁( also ▁considered ▁negative ) ▁Gra de ▁ 2 ▁- ▁Con fl uent ▁pap ules ▁form ▁ind ur ated ▁ring ▁( pos itive ) ▁Gra de ▁ 3 ▁- ▁Central ▁filling ▁to ▁form ▁disc ▁( pos itive ) ▁Gra de ▁ 4 ▁- ▁Disc ▁> 1 0   mm ▁with ▁or ▁without ▁bl ister ing ▁( strong ly ▁positive ) ▁ ▁Gr ades ▁ 1 ▁and ▁ 2 ▁could ▁result ▁from ▁previous ▁B CG ▁or ▁av ian ▁t uber cul osis , ▁rather ▁than ▁human ▁T B ▁in fection . ▁ ▁Children ▁who ▁were ▁found ▁to ▁have ▁a ▁grade ▁ 3 ▁or ▁ 4 ▁reaction ▁were ▁referred ▁for ▁X - ray ▁and ▁follow - up . ▁ ▁For ▁interpretation ▁of ▁the ▁test , ▁see ▁T uber cul osis ▁diagn osis . ▁ ▁Other ▁tests ▁The ▁equivalent ▁Mant oux ▁test ▁positive ▁levels ▁done ▁with ▁ 1 0 ▁T U ▁(