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Background: In 2022, the WHO recommended the 6-month regimens BPaL (bedaquiline + pretomanid + linezolid) and BPaLM (BPaL + moxifloxacin) as treatment options for most forms of drug-resistant TB. SLASH-TB estimates the cost-saving and cost-effectiveness for the healthcare system and patients when a country switches from current standard-of-care treatment regimens to BPaL/BPaLM., Methodology: Country data from national TB programmes (NTP) are used to calculate the costs for all regimens and treatment outcomes. Where BPaL/BPaLM is not currently used, clinical trial outcomes data are used to estimate cost-effectiveness. DALYs are calculated using the Global Burden of Disease (GBD) database., Results: We present the results of four countries that have used the tool and shared their data. When shorter and longer regimens are replaced with BPaL/BPaLM, the savings per patient treated in Pakistan, the Philippines, South Africa, and Ukraine are $746, $478, $757, and $2,636, respectively. An increased number of patients would be successfully treated with BPaL/BPaLM regimens, with 411, 1,025, 1,371 and 829 lives saved and 20,179, 27,443, 33,384 and 21,924 DALYs averted annually in the four countries, respectively., Conclusion: Through BPaL/BPaLM regimens, drug-resistant TB treatment has become more effective, shorter, less burdensome for patients, cheaper for both health systems and patients, and saves more lives., (© 2024 The Authors.)

Background: Bedaquiline improves outcomes of patients with rifampicin-resistant and multidrug-resistant (MDR) tuberculosis; however, emerging resistance threatens this success. We did a cross-sectional and longitudinal analysis evaluating the epidemiology, genetic basis, and treatment outcomes associated with bedaquiline resistance, using data from South Africa (2015-19)., Methods: Patients with drug-resistant tuberculosis starting bedaquiline-based treatment had surveillance samples submitted at baseline, month 2, and month 6, along with demographic information. Culture-positive baseline and post-baseline isolates had phenotypic resistance determined. Eligible patients were aged 12 years or older with a positive culture sample at baseline or, if the sample was invalid or negative, a sample within 30 days of the baseline sample submitted for bedaquiline drug susceptibility testing. For the longitudinal study, the first surveillance sample had to be phenotypically susceptible to bedaquiline for inclusion. Whole-genome sequencing was done on bedaquiline-resistant isolates and a subset of bedaquiline-susceptible isolates. The National Institute for Communicable Diseases tuberculosis reference laboratory, and national tuberculosis surveillance databases were matched to the Electronic Drug-Resistant Tuberculosis Register. We assessed baseline resistance prevalence, mutations, transmission, cumulative resistance incidence, and odds ratios (ORs) associating risk factors for resistance with patient outcomes., Findings: Between Jan 1, 2015, and July 31, 2019, 8041 patients had surveillance samples submitted, of whom 2023 were included in the cross-sectional analysis and 695 in the longitudinal analysis. Baseline bedaquiline resistance prevalence was 3·8% (76 of 2023 patients; 95% CI 2·9-4·6), and it was associated with previous exposure to bedaquiline or clofazimine (OR 7·1, 95% CI 2·3-21·9) and with rifampicin-resistant or MDR tuberculosis with additional resistance to either fluoroquinolones or injectable drugs (pre-extensively-drug resistant [XDR] tuberculosis: 4·2, 1·7-10·5) or to both (XDR tuberculosis: 4·8, 2·0-11·7). Rv0678 mutations were the sole genetic basis of phenotypic resistance. Baseline resistance could be attributed to previous bedaquiline or clofazimine exposure in four (5·3%) of 76 patients and to primary transmission in six (7·9%). Odds of successful treatment outcomes were lower in patients with baseline bedaquiline resistance (0·5, 0·3-1). Resistance during treatment developed in 16 (2·3%) of 695 patients, at a median of 90 days (IQR 62-195), with 12 of these 16 having pre-XDR or XDR., Interpretation: Bedaquiline resistance was associated with poorer treatment outcomes. Rapid assessment of bedaquiline resistance, especially when patients were previously exposed to bedaquiline or clofazimine, should be prioritised at baseline or if patients remain culture-positive after 2 months of treatment. Preventing resistance by use of novel combination therapies, current treatment optimisation, and patient support is essential., Funding: National Institute for Communicable Diseases of South Africa., Competing Interests: Declaration of interests NAI reports partial support from Janssen Pharmaceuticals to the institution for the consumables used for bedaquiline drug susceptibility testing. All other authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Substance use (SU) is associated with poor rifampicin-resistant tuberculosis (RR-TB) treatment outcomes. In 2017, a SBIRT (SU screening-brief intervention-referral to treatment) was integrated into routine RR-TB care in Khayelitsha, South Africa. This was a retrospective study of persons with RR-TB who were screened for SU between 1 July 2018 and 30 September 2020 using the ASSIST (Alcohol, Smoking and Substance Involvement Screening Test). Here we describe outcomes from this program. Persons scoring moderate/high risk received a brief intervention and referral to treatment. Overall, 333 persons were initiated on RR-TB treatment; 38% ( n = 128) were screened for SU. Of those, 88% ( n = 113/128) reported SU; 65% ( n = 83/128) had moderate/high risk SU. Eighty percent ( n = 103/128) reported alcohol use, of whom 52% ( n = 54/103) reported moderate/high risk alcohol use. Seventy-seven persons were screened for SU within ≤2 months of RR-TB treatment initiation, of whom 69%, 12%, and 12% had outcomes of treatment success, loss to follow-up and death, respectively. Outcomes did not differ between persons with no/low risk and moderate/high risk SU or based on the receipt of naltrexone ( p > 0.05). SU was common among persons with RR-TB; there is a need for interventions to address this co-morbidity as part of "person-centered care". Integrated, holistic care is needed at the community level to address unique challenges of persons with RR-TB and SU.

Background: Limited data exist on the use of bedaquiline and delamanid in adolescents with rifampicin-resistant tuberculosis (RR-TB). We describe RR-TB treatment of adolescents (10-19 years) with injectable-free regimens containing these drugs in Khayelitsha, South Africa., Methods: This retrospective study included adolescents initiating injectable-free RR-TB treatment regimens containing bedaquiline and/or delamanid from February 2015 to June 2018. We report adverse events (AEs) of interest, sputum culture conversion (SCC), and final end-of-treatment outcomes., Findings: Twenty-two patients were included; median age at treatment initiation was 17 years (interquartile range [IQR] 15-18), and six (27%) were HIV-positive (median CD4 count 191 cells/mm3 [IQR 157-204]). Eight (36%) patients had RR-TB with fluoroquinolone resistance; ten (45%), eight (36%), and four (18%) patients received regimens containing bedaquiline, delamanid, or the combination of bedaquiline and delamanid, respectively. The median durations of exposure to bedaquiline and delamanid were 5·6 (IQR 5·5-8·4) and 9·4 (IQR 5·9-14·4) months, respectively. There were 49 AEs of interest which occurred in 17 (77%) patients. Fourteen (64%) patients had pulmonary TB with positive sputum cultures at bedaquiline and/or delamanid initiation; among these SCC at month 6 was 79%. Final end-of-treatment outcomes for the 22 adolescent were: 17 (77%) successfully treated, two (9%) lost-to-follow-up, two (9%) treatment failed, and one (5%) died., Interpretation: This study found that injectable-free regimens containing bedaquiline and/or delamanid in a programmatic setting were effective and well tolerated in adolescents and should be routinely provided for RR-TB treatment in this age group as recommended by the World Health Organisation., Competing Interests: We declare no competing interests., (© 2020 Published by Elsevier Ltd.)

Background: Bedaquiline is used as a substitute for second-line injectable (SLI) intolerance in the treatment of multidrug-resistant (MDR) tuberculosis, but the efficacy and safety of this strategy is unknown., Methods: In this retrospective cohort study adults receiving bedaquiline substitution for MDR tuberculosis therapy, plus a matched control group who did not receive bedaquiline, were identified from the electronic tuberculosis register in the Western Cape Province, South Africa. The primary outcome measure was the proportion of patients with death, loss to follow-up, or failure to achieve sustained culture conversion at 12 months of treatment., Results: Data from 162 patients who received bedaquiline substitution and 168 controls were analyzed; 70.6% were infected with human immunodeficiency virus. Unfavorable outcomes occurred in 35 of 146 (23.9%) patients in the bedaquiline group versus 51 of 141 (36.2%) in the control group (relative risk, 0.66; 95% confidence interval, .46 -.95). The number of patients with culture reversion was lower in those receiving bedaquiline (1 patient; 0.8%) than in controls (12 patients; 10.3%; P = .001). Delayed initiation of bedaquiline was independently associated with failure to achieve sustained culture conversion (adjusted odds ratio for every 30-day delay, 1.5; 95% confidence interval, 1.1-1.9). Mortality rates were similar at 12 months (11 deaths in each group; P = .97)., Conclusions: Substituting bedaquiline for SLIs in MDR tuberculosis treatment resulted in improved outcomes at 12 months compared with patients who continued taking SLIs, supporting the use of bedaquiline for MDR tuberculosis treatment in programmatic settings., (© The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Background: Self-administered treatment (SAT), a differentiated model of care for rifampicin-resistant tuberculosis (RR-TB), might address adherence challenges faced by patients and health care systems. This study explored patient, health-care worker (HCW) and community care worker (CCW) perspectives on a SAT pilot programme in South Africa, in which patients were given medication to take at home with the optional support of a CCW., Methods: We conducted a mixed-methods study from July 2016-June 2017. The quantitative component included semi-structured questionnaires with patients, HCWs and CCWs; the qualitative component involved in-depth interviews with patients enrolled in the pilot programme. Interviews were conducted in isiXhosa, translated, transcribed and manually coded., Results: Overall, 27 patients, 12 HCWs and 44 CCWs were enrolled in the quantitative component; nine patients were also interviewed. Of the 27 patients who completed semi-structured questionnaires, 22 were HIV-infected and 17 received a monthly supply of RR TB treatment. Most HCWs and CCWs (10 and 32, respectively) understood the pilot programme; approximately half (n = 14) of the patients could not correctly describe the pilot programme. Overall, 11 and 41 HCWs and CCWs reported that the pilot programme promoted treatment adherence. Additionally, 11 HCWs reported that the pilot programme relieved pressure on the clinic. Key qualitative findings highlighted the importance of a support person and how the flexibility of SAT enabled integration of treatment into their daily routines and reduced time spent in clinics. The pilot programme was also perceived to allow patients more autonomy and made it easier for them to manage side-effects., Conclusion: The SAT pilot programme was acceptable from the perspective of patients, HCWs and CCWs and should be considered as a differentiated model of care for RR-TB, particularly in settings with high burdens of HIV, in order to ease management of treatment for patients and health-care providers., Competing Interests: The authors have declared that no competing interests exist.

Experience with delamanid (Dlm) is limited, particularly among HIV-positive individuals. We describe early efficacy and safety data from a programmatic setting in South Africa.This was a retrospective cohort study of patients receiving Dlm-containing treatment regimens between November 2015 and August 2017. We report 12-month interim outcomes, sputum culture conversion (SCC) by months 2 and 6, serious adverse events (SAEs) and QT intervals corrected using the Frederica formula (QTcF).Overall, 103 patients were initiated on Dlm; 79 (77%) were HIV positive. The main indication for Dlm was intolerance to second-line anti-tuberculosis (TB) drugs (n=58, 56%). There were 12 months of follow-up for 46 patients; 28 (61%) had a favourable outcome (cure, treatment completion or culture negativity). Positive cultures were found for 57 patients at Dlm initiation; 16 out of 31 (52%) had SCC within 2 months and 25 out of 31 (81%) within 6 months. There were 67 SAEs reported in 29 patients (28%). There were four instances of QTcF prolongation >500 ms in two patients (2%), leading to permanent discontinuation in one case; however, no cardiac arrhythmias occurred.This large cohort of difficult-to-treat patients receiving Dlm for rifampicin-resistant TB treatment in a programmatic setting with high HIV prevalence had favourable early treatment response and tolerated treatment well. Dlm should remain available, particularly for those who cannot be treated with conventional regimens or with limited treatment options., Competing Interests: Conflict of interest: None declared., (Copyright ©ERS 2018.)

In patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), expression of the hematopoietic stem cell marker CD34 has been associated with a poorer prognosis. CD34 is usually analyzed by flow cytometry (FC), but may also be analyzed using immunohistochemistry (IH). The present study was undertaken to compare these 2 methods. Bone marrow from 16 patients with MDS and 12 with AML and from 12 healthy young volunteers was studied. The expression of CD34 was analyzed with FC on fresh bone marrow cells and with IH on sections of paraffin-embedded bone marrow. The correlation between FC and IH was good both for patients with MDS (p<0.0001) and AML (p<0.01). However, in patients with a high number of CD34-positive cells, the FC method seemed to result in a higher percentage of positive cells compared to the IH method. In normal bone marrow, the ratio between the percentage of CD34-positive cells and the percentage of bone marrow blasts was approximately 0.8. In the whole group of MDS patients, this ratio was 1:1, while in patients with refractory anemia (RA) and ring sideroblastic anemia (RAS) it was 1.6. Patients with MDS differed significantly from patients with de novo AML, who showed a ratio of only 0.23 (p<0.01). We conclude that the FC and IH methods for measuring expression of CD34 are well-correlated in MDS and reasonably well correlated in AML. A stem cell phenotype is more commonly expressed on precursor cells from patients with MDS than from patients with AML.

Patients with myelodysplastic syndromes (MDS) comprise an extremely heterogeneous group. There is a need for decision models both for predicting the natural course of the disease and the outcomes of different treatment alternatives. In 102 consecutive patients with MDS or acute myelogenous leukemia (AML) following MDS, pre-treatment variables were studied in relation to the response to treatment with low-dose ara-C. Thirty patients (29%) responded with either a complete remission or a significant rise in the hemoglobin level. For the remaining 71%, the treatment was ineffective and in some cases hazardous. The factors associated with a poor response to treatment could be divided into two groups: one included low platelet counts and the presence of chromosomal aberrations, both signs of progressive MDS with a short survival, and the other comprised morphological findings, indicating ineffective hemopoiesis. Patients with platelet counts > 150 x 10(9)/l had a response rate of 55%, compared to 24% in patients with subnormal platelet counts. Logistic regression identified low bone marrow cellularity, absence of ring sideroblasts and < 2 chromosomal aberrations as predictors of a favourable response in patients with platelet counts < 150 x 10(9)/l. These factors and the platelet count were combined in a predictive model which divided patients into three groups with different probabilities of response: one favourable (38% of the patients), with a response rate of > 50%; a second, intermediate group (33% of the patients), with a response rate of 24%; and a third, unfavourable group (29% of the patients) with only 3% responses.(ABSTRACT TRUNCATED AT 250 WORDS)

The response to treatment with low-dose ara-C was studied in 102 consecutive patients; 79 with myelodysplastic syndrome (MDS) and 23 with acute myelogenous leukaemia (AML) following MDS. The aim was to find variables that could predict the response to treatment. All patients had clinical symptoms related to cytopenia. Peripheral blood values, bone marrow morphology histology and chromosomes were analysed before the start of treatment. The median survival of the patients was 9 months and a poor survival was predicted by advanced age, low platelet counts, the presence of pseudo-Pelger morphology and > or = 2 chromosomal aberrations. Thirty patients (29%) responded with either a complete remission or a significant increase in haemoglobin level. For the remaining 71%, the treatment was ineffective and in some cases hazardous. The factors associated with a poor response to treatment could be divided into two groups: one included low platelet counts and the presence of chromosomal aberrations, both signs of progressive MDS with a short survival, and the other comprised morphological findings, indicating ineffective haemopoiesis. Patients with platelet counts > 150 x 10(9)/l had a response rate of 55% compared to 23.5% in patients with subnormal platelet counts. Logistic regression identified low bone marrow cellularity, absence of ring sideroblasts and < 2 chromosomal aberrations as predictors of a favourable response in patients with platelet counts < 150 x 10(9)/l. These factors and the platelet count were combined in a predictive model which can divide patients into three groups with different probabilities of response: a favourable group, 38.6% of the patients, with a response rate of > 50%, an intermediate group, 32.7% of the patients, with a response rate of 24%, and an unfavourable group, 28.7% of the patients, with only 3% responses. While low-dose ara-C is an effective treatment for some patients, it is ineffective and hazardous for others. We present a model that can facilitate therapeutic decision making in two-thirds of patients with MDS and MDS-AML by identifying patients who should not be treated with low-dose ara-C as well as patients with a relatively high probability of response.

Some human tumors have been found to induce proliferative lesions in the squamous epithelium in organs remote from the primary tumor. This phenomenon was explored in the present animal model. After a single injection of 3H-thymidine, the proportion of DNA synthesizing basal and parabasal esophageal cells as well as the pace of intraepithelial cell migration was assessed in 124 C57Bl mice. The uterine cervix of 57 animals had been painted topically with 3,4 benzo(a)pyrene for 5 months, or with the vehicle acetone (44 animals), while 23 animals remained untreated. Groups of animals were killed from 8 hours to 10 days following a single pulse labelling. The proportion of DNA synthesizing basal and parabasal esophageal cells and of their daughter cells (as deduced by observations at various time intervals) was similar in animals harbouring neoplasias of the uterine cervix, in those treated with benzo(a)pyrene but having histologically normal cervical epithelium, in acetone treated as well as in untreated controls. Thus, in the model used herein, we failed to demonstrate increased cell proliferation in the esophageal mucosa of animals having a squamous cell neoplasia in the uterine cervix. The method appears, however, sensitive enough to register ongoing cell proliferation patterns and will be applied to the study of other experimentally induced tumors.

Thirty-four patients with MDS or AML following MDS were studied with regard to survival, peripheral blood values and bone marrow morphology. The effects of 1,25 dihydroxyvitamin D3 (D3) on differentiation (NBT positivity) and proliferation (3H-thymidine incorporation) were studied in suspension cultures of bone marrow cells. Twelve bone marrow donors served as controls. Normal cells showed spontaneous differentiation in vitro, but only 2/12 were induced to differentiation by D3. Myelodysplastic cells did not differentiate spontaneously, but cells from 18/34 patients differentiated after incubation with D3. Normal cells showed increased proliferation, myelodysplastic cells showed a heterogeneous response and leukemic cells reacted with decreased proliferation after D3 incubation. Poor survival was associated with low platelet counts, high percentage of bone marrow blasts (BM blast %), low spontaneous in vitro proliferation and absence of hypogranulation of myeloid cells. Platelet counts and hypogranulation retained their predictive value in a multi-variate analysis. Progression to AML was predicted by a high BM blast % and low scores for erythroid and total dysplasia. In conclusion, the pattern of in vitro proliferation showed prognostic value while the pattern of vitamin D3-induced differentiation failed to correlate to other parameters. An estimation of bone marrow dysplasia can be used to predict the development of AML. Our results add to the information about the biology of MDS and may be important for the evaluation of therapeutic trials.

Autoradiograms of histologic slides of 58 human cone specimens with dysplasia and carcinoma in situ were analyzed after tissue samples were incubated with labeled RNA precursors. Both the vertical and lateral distributions of labeled cells were rather uniform in the major part of the epithelium, which suggested that the tissue remained metabolically active during incubation. Only the uppermost epithelial cells in heavily labeled areas were devitalized as deduced by the morphologic appearance of the cells, the absence of labeling in the cells, the trypan blue exclusion test, and the trypsin digestion test. The viability of large epithelial areas suggested that the previously reported focal distribution of proliferating and nonproliferating areas in the cervical epithelium is a genuine phenomenon and not the result of focal epithelial devitalization acquired during incubation.

Histological preparations of the rectal mucosa were analyzed quantitatively in 51 patients with chronic ulcerative colitis. Four histological variables were recorded: the diameter (minor axis) of the lumen of 10 consecutive (transversally cut) glands, the interglandular linear distance between 10 consecutive glands, the number of glands at high power field examination, and the number of nuclei in 10 consecutive areas of lamina propria. The most important feature found to differentiate colitic from noncolitic patients was the diameter of the lumen of the rectal glands. The sum of the values of the four variables has demonstrated that 94% of the colitic patients had scores of 22 or more. Previous work showed that only 0.8% of 124 noncolitic patients had a similar score.

Quantitative analysis of histological preparations of the rectal mucosa were carried out in 52 patients with gastrointestinal symptoms. Follow-up investigation demonstrated no signs of chronic inflammatory bowel disease. The variables recorded in the histological preparations in the 52 patients were the diameter (minor axis) of 10 consecutive, transversally cut glands, the space of lamina propria between glands, the number of glands per high-power field, and the number of nuclei in 10 consecutive areas of lamina propria (between glands). The histological state of the rectal mucosa in individual patients was quantitatively defined as the score resulting from the sum of the values in each of the above-mentioned variables. Similarly to the rectal mucosa from asymptomatic patients, the rectal mucosa from the 52 symptomatic patients had scores of 21 or less. These composite data form the basis for a comparative quantitative study of the rectal mucosa from patients with various chronic inflammatory conditions of the rectum.

The intratumoral migration of tritiated thymidine ([3H]dThd)-labeled cells was recorded at various intervals (from 1 to 240 hr) in squamous invasive carcinomas of the cervix in 25 inbred C57Bl mice. Carcinomas were induced by local application of benzo[a]pyrene for 5 months. This treatment was discontinued 7 days before the animals were killed. Cells were labeled by a single ip injection of 6 muCi [3H]dThd/g body weight. The tumors were divided by the aid of an ocular scale into three equal compartments: a peripheral zone, an intermediate zone, and a central zone. Many densely (initially) labeled cells were present in the peripheral and intermediate zones 1-48 hours after the injection of isotope, but these cells decreased in number in the intermediate zone and had disappeared from the peripheral zone by 96 hours. Conversely, densely labeled cells were absent in the center of the tumor during the first 24 hours, but they were recorded in large numbers at 48 hours. It was concluded that in addition to already known mechanisms of cell migration in solid tumors (e.g., invasion of the surrounding normal tissue, intravascular migration, migration toward the center of individual tumor nests, and cell exfoliation), there is intratumoral migration of cells toward the center in cervical carcinomas in mice.

To investigate whether the amount of tissue removed at conization could influence the frequency of inadequate excision of cervical atypias, 354 cone specimens were measured. The data indicate that the frequency of lesions incompletely removed at conization increased with decreasing size (ie. length and volume) of the specimen. The parameters influencing the detection of epithelial atypias at the surgical margin of the specimens are discussed. A plea is made for international standardization in reporting results of conization (size of cone and number of sections) in order to permit objective comparison between clinics of the results of the conization procedure.

A model system of 85% exfoliated normal human cervicovaginal squamous cells, 15% exfoliated rodent t-mor cells and acellular, viscous, mucus-like material was used to investigate the distribution of cells on smear preparations. Smears were made by the same individual with wooden spatulas, using traditional smearing motions. The presence or absence of normal squamous cervicovaginal cells and of tumor cells in ten randomly distributed areas was recorded. Smears made with counterclockwise circular motions contained the largest number of tumor cells, and those with zigzag strokes contained the least. Independent of the motion employed, the largest number of tumor cells was found in ring 9 and the lowest in rings 4 and 10. Some of the factors influencing the accumulation of tumor cells in certain areas of the slide may be: unequal pressure of the spatula during smearing, variations in the angle between the instrument and the surface of the slide and the displacement of tumor cells to certain areas of the preparation by overlapping smearing.

The migration of tritiated thymidine ([3H]dThd)-labeled cells toward the epithelial surface was recorded at various intervals (from 1 to 240 hr) in the normal and atypical cervical epithelial of 127 C57BL mice. Cervical atypias were induced by local application of 3,4-benzo[a]pyrene for 5 months9 This treatment was discontinued 7 days before the animals were killed. Cells were labeled by a single ip injection of 6 muCi [3H]dThd/g body weight. The disappearance of heavily labeled cells in normal animals 96 hours after the pulse and in solvent-treated controls after 144 hours suggested that the original labeled cells had been exfoliated. However, cervical atypias showed heavily labeled cells as much as 240 hours after the [3H]dThd incorporation. Universal epithelial labeling (suggesting repopulation by daughter cells) usually occurred 24--48 hours after pulse labeling in normal and control animals but occurred after 96--240 hours in animals with atypical epithelium. On the basis of these results, the pace of both cellular intraepithelium transmigration and of epithelial repopulation by atypical daughter cells is substantially retarded during the early stages of cervical carcinogenesis.

An attempt was made to study preleukemic changes in bone marrow cell proliferation. Seven patients with hypercellular marrows and aregenerative anemia were studied. Five of them could be followed to autopsy, several years after the kinetic studies; all died with a picture of leukemia. Total bone marrow cell numbers, erythroblast generation times, and erythrocyte production were estimated with 59Fe. Despite hypercellularity, the total erythroblast number was not significantly increased. Erythrocyte production and life span were both decreased, and erythroblast generation time were significantly longer than normal.