Thrombopoiesis in itp and hiv-itp and in response to intravenous gammaglobulin (ivig)treatment
Bronchoalveolar Lavage Fluid
Currently, diagnosis of immune thrombocytopenic purpura (ITP)is based on low platelet count and exclusion of clinical conditions rather than demonstration of a laboratory finding ie +platelet antibodies. This study applied the thiazole orange assay of reticulated platelets (RP) to classsical ITP and thrombocytopenia associated with HIV infection (HIV-ITP). Data of 96 ITP patients, (1 sample/patient), gave low PC with both high & low % reticulated platelets (RP). -15% had % RP below(L)normal range: 0.7 ±0.7 %RP associated with a mean PC of 141±220xlO"/L; 33% were normal range (N), 1.2±1.2 %RP with 80±100xl09/L PC & 53% were higher at 3.3±4.3 %RP with PC of 65+94x10'/L.3 patients tested within 24h of IVIG had circulating PC with lower RP than expected: PC/L increased 15.75, 6.8 or 4.6X, corresponding RPxlO'/L (RP/L) increased to 4.5 & l .88X or decreased to 0.23X, suggesting dilution by an older platelet population. 4 patients measured within 10 days of IVIG gave: Before IVIG: PC=9±11,5; %RP=9±4.6; RP/L=0.67±0.58. After IVIG: PC=115±9I ; %RP=1.8±1.3; RP/L=2.8+2.6. TPO levels of 21 ITP patients were 235± 124 (range 100-654) pg/mL compared to the normal level of 123 (range 21 -407 ) pg/mL, but there was no correlation with PC, %RP or RP/L. PC<30 PC<30 PC<30 PC>30 PC>30 PC>30 %RP RP/L L&N %RP "RP RP/L L&N %RP ITP. n=93 6.1±4.4 0.7±0.7 9/38,24" 2.9+2.9 3.3±0.7 35/55,64" HIV-ITP, n=22 5.7±5.6 0.8±1.0 4/11,36" 4.0±3 1.911.6 6/11,54" In this study (1 sample/patient) HIV-ITP patients had more profound thrombocytopenia (PC=31±20xlO'/L, n=23) than did ITP patients (82±120xlO'/L, n=96) with p<0.05 by anova and (-test. Some serial samples of HIV-ITP patients showed high %RP and low PC similar to ITP, suggesting destruction. Others showed the low %RP & low PC profile of impaired thrombopoiesis. Responses to IV gammaglobulins were like those of ITP patients. Overall ITP and HIV-ITP patients were heterogeneous in terms of their thrombopoiesis and remarkably similar in their heterogeneity. Preliminary studies show estimation of RP as a measure of thrombopoiesis may predict responses to treatments whose primary effect is interference with platelet destruction.